%% Papers Published
@article{fds245070,
Author = {Levi, M and Armstrong, T and Baranger, H and Bregman, M and Mael, D and Strait, J and Sulak, L and Bowen, T and Pifer, B and Polakos, P and Bradner, H and Parvulescu, A and Jones, H and Learned,
J},
Title = {EXPERIMENTAL STUDIES OF THE ACOUSTIC SIGNATURE OF PROTON
BEAMS TRAVERSING FLUID MEDIA.},
Journal = {IEEE Transactions on Nuclear Science},
Volume = {NS 25},
Number = {1},
Pages = {325-332},
Publisher = {Institute of Electrical and Electronics Engineers
(IEEE)},
Year = {1977},
url = {http://dx.doi.org/10.1109/TNS.1978.4329325},
Abstract = {This work establishes that a detectable sonic signal is
produced by protons while traversing through or stopping in
a fluid medium. Experiments exploring the global
characteristics of both the acoustic generation mechanism
and the radiation pattern performed at three different
accelerators. The results are consistent with a simple
thermal model for the transformation of the energy of moving
charged particles into acoustic energy. This phenomenon
could be exploited in several applications: (1) as a charged
particle monitor in accelerator beams, (2) as a heavy ion
detector sensitive to nuclear charge, e. g. , in measuring
the cosmic ray isotope as an inexpensive shower detector in
massive neutrino detectors at the next generation of high
energy accelerators, e. g, the Fermilab energy doubler and
(4) as the shower calorimeter (and perhaps the muon
detector) in massive deep underwater detectors of cosmic
neutrino and muon interactions.},
Doi = {10.1109/TNS.1978.4329325},
Key = {fds245070}
}
@article{fds245069,
Author = {Sulak, L and Armstrong, T and Baranger, H and Bregman, M and Levi, M and Mael, D and Strait, J and Bowen, T and Pifer, AE and Polakos, PA and Bradner, H and Parvulescu, A and Jones, WV and Learned,
J},
Title = {Experimental studies of the acoustic signature of proton
beams traversing fluid media},
Journal = {Nuclear Instruments and Methods},
Volume = {161},
Number = {2},
Pages = {203-217},
Publisher = {Elsevier BV},
Year = {1979},
Month = {May},
ISSN = {0029-554X},
url = {http://dx.doi.org/10.1016/0029-554X(79)90386-0},
Abstract = {Recent experiments at Brookhaven National Laboratory and
Harvard University demonstrate that a detectable sonic
signal is produced by energetic proton beams while
traversing a fluid medium. The observed acoustic wave agrees
with the predictions of a thermal expansion model. Results
are inconsistent with any significant contribution from
either microbubble implosion or molecular dissociation, two
other suggested means of sonic production. Frequency and
amplitude distributions, radiation patterns, temperature,
pressure, and medium dependencies are explored. This
phenomenon may have immediate applications in beam
monitoring and in detecting energetic heavy ions. Signal
thresholds may be enough to permit detection of particle
showers induced by single particles at the next generation
of high energy accelerators or from high energy cosmic rays.
The inexpensive transducers and long sonic transmission
lengths obtainable in liquids suggest that high energy
particle detectors may be feasible with masses many orders
of magnitude greater than those currently in use. ©
1979.},
Doi = {10.1016/0029-554X(79)90386-0},
Key = {fds245069}
}
@article{baranger:7349,
Author = {Baranger, HU and Wilkins, JW},
Title = {Ballistic electrons in an inhomogeneous submicron structure:
Thermal and contact effects},
Journal = {Physical Review B},
Volume = {30},
Number = {12},
Pages = {7349-7351},
Publisher = {American Physical Society (APS)},
Year = {1984},
Month = {January},
ISSN = {0163-1829},
url = {http://link.aps.org/abstract/PRB/v30/p7349},
Keywords = {SEMICONDUCTOR MATERIALS; TRANSPORT THEORY; ELECTRON SPECTRA;
MICROSTRUCTURE; DIFFUSION; ELECTRIC CONTACTS; DEBYE LENGTH;
BOLTZMANN EQUATION; TEMPERATURE EFFECTS},
Abstract = {For a simple submicron semiconductor structure we have
calculated exactly the electron distribution f(v,x) within a
relaxation-to-local-equilibrium assumption for the collision
term of the Boltzmann equation. This is the first
calculation of the electron distribution in an inhomogeneous
semiconductor. Large applied voltages produce a substantial
ballistic peak in f(v,x). But at all voltages contact
inhomogeneities and local heating (and cooling) produce an
I-V characteristic only weakly dependent on the scattering
rate. © 1984 The American Physical Society.},
Doi = {10.1103/PhysRevB.30.7349},
Key = {baranger:7349}
}
@booklet{Baranger85,
Author = {Baranger, HU and Wilkins, JW},
Title = {Ballistic electrons in a submicron structure: The
distribution function and two valley effects},
Journal = {Physica B+C},
Volume = {134},
Number = {1-3},
Pages = {470-474},
Publisher = {Elsevier BV},
Year = {1985},
Month = {January},
ISSN = {0378-4363},
url = {http://dx.doi.org/10.1016/0378-4363(85)90389-4},
Abstract = {We have solved the Boltzman equation for a submicron
N+-N--N+ GaAs structure within a two-valley model using
energy-dependent relaxation times. Ballistic electrons
produce a large peak in the velocity-distribution function
throughout much of the N- region. Transfer of electrons from
the lower to upper valley in the N- layer causes an
accumulation of charge near the collecting N+ region.
Transfer of electrons back from the upper to the lower
valley in the collecting N+ region creates two new peaks in
the distribution function which we call ballistic electron
echoes. © 1985.},
Doi = {10.1016/0378-4363(85)90389-4},
Key = {Baranger85}
}
@booklet{Baranger85a,
Author = {Baranger, HU and MacDonald, AH and Leavens, CR},
Title = {Heterocontact effects in point-contact electron-phonon
spectroscopy of the alkali metals.},
Journal = {Physical review. B, Condensed matter},
Volume = {31},
Number = {10},
Pages = {6197-6206},
Year = {1985},
Month = {May},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/9935491},
Doi = {10.1103/physrevb.31.6197},
Key = {Baranger85a}
}
@booklet{Stanton86,
Author = {Stanton, CJ and Baranger, HU and Wilkins, JW},
Title = {Analytic Boltzmann equation approach for negative
differential mobility in two-valley semiconductors},
Journal = {Applied Physics Letters},
Volume = {49},
Number = {3},
Pages = {176-178},
Publisher = {AIP Publishing},
Year = {1986},
Month = {December},
ISSN = {0003-6951},
url = {http://dx.doi.org/10.1063/1.97216},
Abstract = {We present results for the negative differential mobility
and the distribution function in GaAs and InP for electric
fields less than 40 kV/cm based on the analytic solution of
the Boltzmann equation for a model with two valleys and
three relaxation times. Using the measured low field
mobility, lower valley mass, and valley separation energy Δ
while adjusting three upper valley parameters, we obtain
good agreement with the experimental velocity-field curves.
The distribution function in the lower valley shows
structure at energies ≊Δ due to the intervalley
scattering.},
Doi = {10.1063/1.97216},
Key = {Stanton86}
}
@article{baranger:1708,
Author = {Baranger, HU and Pelouard, JL and Pône, JF and Castagné,
R},
Title = {Ballistic peaks in the distribution function from
intervalley transfer in a submicron structure},
Journal = {Applied Physics Letters},
Volume = {51},
Number = {21},
Pages = {1708-1710},
Publisher = {AIP Publishing},
Year = {1987},
Month = {January},
ISSN = {0003-6951},
url = {http://link.aip.org/link/?APL/51/1708/1},
Keywords = {GALLIUM ARSENIDES; MONTE CARLO METHOD; SIMULATION;
SEMICONDUCTOR DEVICES; CHARGED–PARTICLE TRANSPORT;
DISTRIBUTION FUNCTIONS},
Abstract = {Using Monte Carlo simulation, we show that ballistic
electrons coupled with intervalley scattering produce peaks
in the distribution function of electrons in submicron
structures. The distribution functions f(v,x) and f(ε,x)
for a submicron N+-N--N+ GaAs structure indicate that
ballistic electrons cause both the dominant peak in f(v,x)
throughout the N- region and additional peaks in f(ε,x)
following transfer from the L valley to the Γ valley. For
low densities and low temperatures (T=77), both ballistic
peaks in f(ε,x) split into several sharp peaks separated in
energy by the optic-phonon energy.},
Doi = {10.1063/1.98551},
Key = {baranger:1708}
}
@article{baranger:1487,
Author = {Baranger, HU and Wilkins, JW},
Title = {Ballistic structure in the electron distribution function of
small semiconducting structures: General features and
specific trends.},
Journal = {Physical review. B, Condensed matter},
Volume = {36},
Number = {3},
Pages = {1487-1502},
Publisher = {APS},
Year = {1987},
Month = {July},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/9942980},
Keywords = {GALLIUM ARSENIDES; HETEROJUNCTIONS; ELECTRONS; DISTRIBUTION
FUNCTIONS; TRANSPORT PROCESSES; HOT ELECTRONS; POISSON
EQUATION; BOLTZMANN EQUATION; RELAXATION TIME; IV
CHARACTERISTIC; MOBILITY},
Doi = {10.1103/physrevb.36.1487},
Key = {baranger:1487}
}
@article{chang:2745,
Author = {Chang, AM and Timp, G and Cunningham, JE and Mankiewich, PM and Behringer, RE and Howard, RE and Baranger, HU},
Title = {Real-space and magnetic-field correlation of
quantum-resistance fluctuations in the ballistic regime in
narrow GaAs-AlxGa},
Journal = {Physical review. B, Condensed matter},
Volume = {37},
Number = {5},
Pages = {2745-2748},
Publisher = {APS},
Year = {1988},
Month = {February},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/9944842},
Keywords = {GALLIUM ARSENIDES; ALUMINIUM ARSENIDES; ONE –
DIMENSIONAL SYSTEMS; WIRES; TRANSPORT PROCESSES; QUANTUM
MECHANICS; HETEROSTRUCTURES; ELECTRIC CONDUCTIVITY;
FLUCTUATIONS; CORRELATIONS; MAGNETIC FIELDS},
Doi = {10.1103/physrevb.37.2745},
Key = {chang:2745}
}
@booklet{Baranger88,
Author = {Baranger, HU and Stone, AD and DiVincenzo, DP},
Title = {Resistance fluctuations in multiprobe microstructures:
Length dependence and nonlocality.},
Journal = {Physical review. B, Condensed matter},
Volume = {37},
Number = {11},
Pages = {6521-6524},
Year = {1988},
Month = {April},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/9943907},
Doi = {10.1103/physrevb.37.6521},
Key = {Baranger88}
}
@article{timp:2081,
Author = {Timp, G and Baranger, HU and deVegvar, P and Cunningham, JE and Howard,
RE and Behringer, R and Mankiewich, PM},
Title = {Propagation around a bend in a multichannel electron
waveguide.},
Journal = {Physical review letters},
Volume = {60},
Number = {20},
Pages = {2081-2084},
Publisher = {APS},
Year = {1988},
Month = {May},
url = {http://www.ncbi.nlm.nih.gov/pubmed/10038252},
Keywords = {MAGNETORESISTANCE; WIRES; FABRICATION; GALLIUM ARSENIDES;
ALUMINIUM ARSENIDES; HETEROSTRUCTURES; SIMULATION; NUMERICAL
ANALYSIS; ONE – DIMENSIONAL SYSTEMS},
Doi = {10.1103/physrevlett.60.2081},
Key = {timp:2081}
}
@article{chang:2695,
Author = {Chang, AM and Chang, TY and Baranger, HU},
Title = {Erratum: Quenching of the Hall resistance in a novel
geometry [Phys. Rev. Lett. [bold 63], 996
(1989)]},
Journal = {Phys. Rev. Lett.},
Volume = {63},
Number = {24},
Pages = {2695-2695},
Publisher = {APS},
Year = {1989},
ISSN = {0031-9007},
url = {http://link.aps.org/abstract/PRL/v63/p2695/s4},
Doi = {10.1103/PhysRevLett.63.2695.4},
Key = {chang:2695}
}
@article{fds304505,
Author = {Chang, AM and Chang, TY and Baranger, HU},
Title = {Erratum: Quenching of the Hall resistance in a novel
geometry (Physical Review Letters (1989) 63, 996
(2695))},
Journal = {Physical Review Letters},
Volume = {63},
Number = {24},
Pages = {2695},
Publisher = {American Physical Society (APS)},
Year = {1989},
Month = {January},
ISSN = {0031-9007},
url = {http://dx.doi.org/10.1103/PhysRevLett.63.2695.4},
Doi = {10.1103/PhysRevLett.63.2695.4},
Key = {fds304505}
}
@booklet{Timp89,
Author = {Timp, G and Mankiewich, PM and deVegvar, P and Behringer, R and Cunningham, JE and Howard, RE and Baranger, HU and Jain,
JK},
Title = {Suppression of the Aharonov-Bohm effect in the quantized
Hall regime.},
Journal = {Physical review. B, Condensed matter},
Volume = {39},
Number = {9},
Pages = {6227-6230},
Publisher = {APS},
Year = {1989},
Month = {March},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/9949054},
Keywords = {GALLIUM ARSENIDES; ALUMINIUM ARSENIDES; HETEROSTRUCTURES;
RINGS; QUANTUM HALL EFFECT; MAGNETORESISTANCE},
Doi = {10.1103/physrevb.39.6227},
Key = {Timp89}
}
@article{baranger:414,
Author = {Baranger, HU and Stone, AD},
Title = {Quenching of the Hall resistance in ballistic
microstructures: A collimation effect.},
Journal = {Physical review letters},
Volume = {63},
Number = {4},
Pages = {414-417},
Publisher = {APS},
Year = {1989},
Month = {July},
url = {http://www.ncbi.nlm.nih.gov/pubmed/10041067},
Keywords = {HALL EFFECT; INHIBITION; MICROSTRUCTURE; MAGNETIC FIELDS;
ONE – DIMENSIONAL SYSTEMS; WIRES; WIDTH; ELECTRIC
PROBES},
Doi = {10.1103/physrevlett.63.414},
Key = {baranger:414}
}
@booklet{Chang89,
Author = {Chang, AM and Chang, TY and Baranger, HU},
Title = {Quenching of the Hall resistance in a novel
geometry.},
Journal = {Physical review letters},
Volume = {63},
Number = {9},
Pages = {996-999},
Publisher = {APS},
Year = {1989},
Month = {August},
url = {http://www.ncbi.nlm.nih.gov/pubmed/10041242},
Keywords = {HALL EFFECT; INHIBITION; GEOMETRY; GALLIUM ARSENIDES;
ALUMINIUM ARSENIDES; HETEROSTRUCTURES; QUANTUM MECHANICS;
ELECTRON DENSITY; ULTRALOW TEMPERATURE; MAGNETIC
FIELDS},
Doi = {10.1103/physrevlett.63.996},
Key = {Chang89}
}
@booklet{Baranger89,
Author = {H. U. Baranger and A. D. Stone},
Title = {Electrical linear-response theory in an arbitrary
magnetic-field - a new fermi-surface formation},
Journal = {Physical Review B},
Volume = {40},
Number = {12},
Pages = {8169 -- 8193},
Year = {1989},
Month = {October},
Key = {Baranger89}
}
@article{baranger:8169,
Author = {Baranger, HU and Stone, AD},
Title = {Electrical linear-response theory in an arbitrary magnetic
field: A new Fermi-surface formation.},
Journal = {Physical review. B, Condensed matter},
Volume = {40},
Number = {12},
Pages = {8169-8193},
Publisher = {APS},
Year = {1989},
Month = {October},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/9991272},
Keywords = {MAGNETIC FIELDS; QUANTUM HALL EFFECT; ELECTRIC CONDUCTORS;
ELECTRON MOBILITY; ELECTRIC CURRENTS; RESPONSE FUNCTIONS;
SEMICONDUCTOR MATERIALS; TRANSPORT PROCESSES},
Doi = {10.1103/physrevb.40.8169},
Key = {baranger:8169}
}
@booklet{Behringer89,
Author = {Behringer, RE and Mankiewich, PM and Timp, G and Howard, RE and Baranger, HU and Cunningham, J and Sampere, S},
Title = {One-dimensional ballistic transport in AlGaAs/GaAs electron
waveguides},
Journal = {Journal of Vacuum Science & Technology B:
Microelectronics Processing and Phenomena},
Volume = {7},
Number = {6},
Pages = {2039-2043},
Publisher = {American Vacuum Society},
Year = {1989},
Month = {November},
ISSN = {1071-1023},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:A1989CG91400147&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {<jats:p>Recently, there has been growing interest in
exploring the limits to scaling of semiconductor devices,
and in understanding their characteristics in the regime
where quantum effects and ballistic transport dominate.
Using high-resolution fabrication techniques on
high-mobility, modulation-doped AlGaAs/GaAs, it is possible
to confine the two-dimensional electron gas (2DEG) to
structures that are smaller than both the inelastic and
elastic scattering lengths, and are comparable in size to
the electron wavelength. The conduction of such a device
should be one dimensional and ballistic. Unlike large
samples, the resistance of these ballistic devices does not
follow classical equations; it is primarily caused by
electron interference and scattering from the geometry of
the sample, not by impurities. On this scale, these
structures behave as electron waveguides not as diffusive
conductors. We have used electron-beam lithography and
high-resolution reaction ion etching to produce samples with
well controlled, complicated geometries. These devices use
either depletion from an etched surface, or the application
of a gate voltage to electrostatically confine the 2DEG to a
narrow conducting channel. Transport measurements exhibit
electron interference effects, nonlocal resistance
fluctuations, resistance that does not scale with length,
and quantization-of-resistance as a function of width and
carrier density. The experiments correspond well to
theoretical calculations of simple electron waveguides, and
show that in these one-dimensional ballistic devices, the
measured resistance is primarily caused by scattering from
the structure of the sample itself.</jats:p>},
Doi = {10.1116/1.584644},
Key = {Behringer89}
}
@article{fds318401,
Author = {BARANGER, HU and STONE, AD},
Title = {SELECTIVE-POPULATION OF MODES IN ELECTRON WAVE-GUIDES - BEND
RESISTANCES AND QUENCHING OF THE HALL RESISTANCE},
Journal = {SCIENCE AND ENGINEERING OF ONE- AND ZERO-DIMENSIONAL
SEMICONDUCTORS},
Volume = {214},
Pages = {121-132},
Publisher = {PLENUM PRESS DIV PLENUM PUBLISHING CORP},
Editor = {BEAUMONT, SP and SOTOMAYORTORRES, CM},
Year = {1990},
Month = {January},
ISBN = {0-306-43417-2},
Key = {fds318401}
}
@booklet{Baranger90a,
Author = {Baranger, HU and Stone, AD},
Title = {Geometrical effects on the Hall resistance in ballistic
microstructures},
Journal = {Surface Science},
Volume = {229},
Number = {1-3},
Pages = {212-215},
Publisher = {Elsevier BV},
Year = {1990},
Month = {April},
ISSN = {0039-6028},
url = {http://dx.doi.org/10.1016/0039-6028(90)90873-7},
Abstract = {We calculate the Hall resistance of four-probe junctions
with unusual geometries similar to those used in recent
experiments. We find a variety of behavior, including
quenching at low magnetic fields and a negative Hall
resistance at low fields. Our results are in excellent
agreement with the experiments and are explained naturally
through the concept of collimation of the electrons in the
leads. In particular, we find that a gradually changing
width is necessary on all four leads in order to produce
good quenching, and that a negative Hall resistance in a
widened cross structure requires both a region of gradual
widening to provide collimation and a region of rapid
widening to reflect the collimated beam. ©
1990.},
Doi = {10.1016/0039-6028(90)90873-7},
Key = {Baranger90a}
}
@article{jalabert:2442,
Author = {Jalabert, RA and Baranger, HU and Stone, AD},
Title = {Conductance fluctuations in the ballistic regime: A probe of
quantum chaos?},
Journal = {Physical review letters},
Volume = {65},
Number = {19},
Pages = {2442-2445},
Publisher = {APS},
Year = {1990},
Month = {November},
url = {http://www.ncbi.nlm.nih.gov/pubmed/10042549},
Keywords = {FLUCTUATIONS; SCATTERING; MAGNETIC FIELDS; CORRELATION
FUNCTIONS; ENERGY; SEMICLASSICAL APPROXIMATION; NUMERICAL
SOLUTION; CLASSICAL MECHANICS; CHAOTIC SYSTEMS; HALL EFFECT;
JUNCTIONS; QUANTUM MECHANICS; TRAJECTORIES; CORRELATION
LENGTH; DISKS},
Doi = {10.1103/physrevlett.65.2442},
Key = {jalabert:2442}
}
@article{fds245049,
Author = {Woodward, TK and Chemla, DS and Bar-Joseph, I and Baranger, HU and Sivco, DL and Cho, AY},
Title = {Sequential vs. coherent tunneling in double barrier diodes
investigated by differential absorption spectroscopy},
Journal = {Technical Digest - International Electron Devices
Meeting},
Pages = {959-962},
Year = {1990},
Month = {December},
Abstract = {The charge distributions in the quantum wells of several
double barrier diodes were measured. It is found that the
ratio of the stored charge to the current is not equal to
the coherent state lifetime and is basically insensitive to
the amount of scattering. It was experimentally demonstrated
that phase breaking collisions take place in the present
structures by observing the energy distribution of the
stored charge in both single and double resonance
structures.},
Key = {fds245049}
}
@article{baranger:11479,
Author = {Baranger, HU},
Title = {Multiprobe electron waveguides: Filtering and bend
resistances.},
Journal = {Physical review. B, Condensed matter},
Volume = {42},
Number = {18},
Pages = {11479-11495},
Publisher = {APS},
Year = {1990},
Month = {December},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/9995452},
Keywords = {WAVEGUIDES; QUANTUM ELECTRONICS; SUPERCONDUCTING WIRES;
ELECTRIC CONDUCTIVITY; LOW TEMPERATURE; HETEROJUNCTIONS;
CHARGED – PARTICLE TRANSPORT; ELECTRONS},
Doi = {10.1103/physrevb.42.11479},
Key = {baranger:11479}
}
@article{fds330535,
Author = {Davies, JH and Nixon, JA and Baranger, HU},
Title = {Potential Fluctuations in Heterostructure
Devices},
Volume = {253},
Pages = {387-397},
Publisher = {Springer US},
Editor = {BEEBY, JL and BHATTACHARYA, PK and GRAVELLE, PC and KOCH, F and LOCKWOOD, DJ},
Year = {1991},
ISBN = {9781468413502},
url = {http://dx.doi.org/10.1007/978-1-4684-1348-9_30},
Doi = {10.1007/978-1-4684-1348-9_30},
Key = {fds330535}
}
@booklet{Nixon91a,
Author = {Nixon, JA and Davies, JH and Baranger, HU},
Title = {Conductance of quantum point contacts calculated using
realistic potentials},
Journal = {Superlattices and Microstructures},
Volume = {9},
Number = {2},
Pages = {187-190},
Publisher = {Elsevier BV},
Year = {1991},
Month = {January},
ISSN = {0749-6036},
url = {http://dx.doi.org/10.1016/0749-6036(91)90280-5},
Abstract = {The quantized conductance of ballistic electrons in narrow
constrictions requires the low scattering rates of a high
mobility 2-dimensional electron gas(2DEG). Despite the
spectacular mobilities of 2DEGs, quantization breaks down
for constrictions longer than about 500 nm, whereas the mean
free path in the ungated 2DEG may exceed 10 μm. We show
that potential fluctuations from a random distribution of
ionised donors modify the guiding potential from the gate in
an unpredictable way. The fluctuations are responsible for
the variability among nominally identical devices. For a
short constriction (200 nm) the conductance can be well
quantized. The accuracy of quantization in a longer
constriction (600 nm) is reduced by scattering from the
random potential of the donors. This occurs when the length
scale of the constriction is greater than that of the
fluctuations. The conductance characteristics depend
strongly on the exact configuration of impurities. In some
cases the random potential causes a resonance in the
channel. © 1991.},
Doi = {10.1016/0749-6036(91)90280-5},
Key = {Nixon91a}
}
@article{fds330534,
Author = {BARANGER, HU},
Title = {TRANSPORT IN ELECTRON WAVE-GUIDES - FILTERING AND BEND
RESISTANCES},
Journal = {COMPUTATIONAL ELECTRONICS},
Pages = {201-206},
Publisher = {KLUWER ACADEMIC PUBLISHERS},
Editor = {HESS, K and LEBURTON, JP and RAVAIOLI, U},
Year = {1991},
Month = {January},
ISBN = {0-7923-9088-1},
Key = {fds330534}
}
@article{behringer:930,
Author = {Behringer, R and Timp, G and Baranger, HU and Cunningham,
JE},
Title = {Quantum-mechanical features in the resistance of a submircon
junction.},
Journal = {Physical review letters},
Volume = {66},
Number = {7},
Pages = {930-933},
Publisher = {APS},
Year = {1991},
Month = {February},
url = {http://www.ncbi.nlm.nih.gov/pubmed/10043943},
Keywords = {WIRES; TEMPERATURE DEPENDENCE; ELECTRON – IMPURITY
INTERACTIONS; MAGNETORESISTANCE; FLUCTUATIONS; DISORDERED
SYSTEMS; HALL EFFECT; FERMI LEVEL; ELECTRON GAS; QUANTUM
MECHANICS; NUMERICAL DATA; HETEROSTRUCTURES},
Doi = {10.1103/physrevlett.66.930},
Key = {behringer:930}
}
@booklet{Nixon91,
Author = {Nixon, JA and Davies, JH and Baranger, HU},
Title = {Breakdown of quantized conductance in point contacts
calculated using realistic potentials.},
Journal = {Physical review. B, Condensed matter},
Volume = {43},
Number = {15},
Pages = {12638-12641},
Publisher = {APS},
Year = {1991},
Month = {May},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/9997071},
Keywords = {QUANTUM WELL STRUCTURES; TRANSPORT THEORY; POINT CONTACTS;
DONORS; IMPURITIES; ELECTRIC CONDUCTIVITY;
HETEROSTRUCTURES},
Doi = {10.1103/physrevb.43.12638},
Key = {Nixon91}
}
@article{woodward:1353,
Author = {Woodward, TK and Chemla, DS and Bar-Joseph, I and Baranger, HU and Sivco, DL and Cho, AY},
Title = {Sequential versus coherent tunneling in double-barrier
diodes investigated by differential absorption
spectroscopy.},
Journal = {Physical review. B, Condensed matter},
Volume = {44},
Number = {3},
Pages = {1353-1356},
Publisher = {APS},
Year = {1991},
Month = {July},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/9999652},
Keywords = {HETEROSTRUCTURES; ABSORPTION SPECTRA; CHARGE DISTRIBUTION;
ELECTRIC CURRENTS; QUANTUM WELL STRUCTURES; TUNNEL
EFFECT},
Doi = {10.1103/physrevb.44.1353},
Key = {woodward:1353}
}
@article{baranger:10637,
Author = {Baranger, HU and DiVincenzo, DP and Jalabert, RA and Stone,
AD},
Title = {Classical and quantum ballistic-transport anomalies in
microjunctions.},
Journal = {Physical review. B, Condensed matter},
Volume = {44},
Number = {19},
Pages = {10637-10675},
Publisher = {APS},
Year = {1991},
Month = {November},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/9999090},
Keywords = {JUNCTIONS; TWO – DIMENSIONAL SYSTEMS; MAGNETIC FIELDS;
TRANSPORT PROCESSES; CLASSICAL MECHANICS; ANOMALOUS
PROPERTIES; BALLISTICS; HALL EFFECT; SCATTERING; INJECTION;
MAGNETORESISTANCE},
Doi = {10.1103/physrevb.44.10637},
Key = {baranger:10637}
}
@booklet{Band92,
Author = {Band, YB and Baranger, HU and Avishai, Y},
Title = {Relationship between resistance, localization length, and
inelastic-scattering length.},
Journal = {Physical review. B, Condensed matter},
Volume = {45},
Number = {3},
Pages = {1488-1491},
Publisher = {APS},
Year = {1992},
Month = {January},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/10001639},
Keywords = {ELECTRIC CONDUCTIVITY; LOCALIZED STATES; INELASTIC
SCATTERING; WIRES; DISTRIBUTION FUNCTIONS; ANALYTICAL
SOLUTION; TEMPERATURE DEPENDENCE; ELASTIC SCATTERING;
TRANSMISSION; REFLECTION; SCATTERING AMPLITUDES; INTEGRAL
EQUATIONS; RANDOM WALK; MEAN FREE PATH},
Doi = {10.1103/physrevb.45.1488},
Key = {Band92}
}
@booklet{Goni92,
Author = {Goñi, AR and Pfeiffer, LN and West, KW and Pinczuk, A and Baranger, HU and Stormer, HL},
Title = {Observation of quantum wire formation at intersecting
quantum wells},
Journal = {Applied Physics Letters},
Volume = {61},
Number = {16},
Pages = {1956-1958},
Publisher = {AIP Publishing},
Year = {1992},
Month = {January},
ISSN = {0003-6951},
url = {http://dx.doi.org/10.1063/1.108375},
Abstract = {We report the first observation of a quantum bound state
formed at the junction of two intersecting quantum wells in
the shape of a T. The atomically precise T junctions are
fabricated by a novel cleaved edge overgrowth process in the
AlGaAs/GaAs system. The identification of bound states with
energies in excess of 20 meV is made by optical emission and
absorption spectroscopy. Such quantum wire states are caused
by the unique confinement of the lowest state wave function
to the region of the T junction.},
Doi = {10.1063/1.108375},
Key = {Goni92}
}
@booklet{Baranger93,
Author = {Baranger, HU and Jalabert, RA and Stone, AD},
Title = {Weak localization and integrability in ballistic
cavities.},
Journal = {Physical review letters},
Volume = {70},
Number = {25},
Pages = {3876-3879},
Year = {1993},
Month = {June},
url = {http://www.ncbi.nlm.nih.gov/pubmed/10053988},
Doi = {10.1103/physrevlett.70.3876},
Key = {Baranger93}
}
@article{baranger:665,
Author = {Baranger, HU and Jalabert, RA and Stone, AD},
Title = {Quantum-chaotic scattering effects in semiconductor
microstructures.},
Journal = {Chaos (Woodbury, N.Y.)},
Volume = {3},
Number = {4},
Pages = {665-682},
Publisher = {AIP},
Year = {1993},
Month = {October},
url = {http://www.ncbi.nlm.nih.gov/pubmed/12780071},
Keywords = {MICROSTRUCTURE; SEMICONDUCTOR MATERIALS; SCATTERING THEORY;
CHAOTIC SYSTEMS; ELECTRIC CONDUCTIVITY; FLUCTUATIONS;
SEMICLASSICAL APPROXIMATION; POWER SPECTRA; TRANSPORT
PROCESSES; SCALING LAWS; POTENTIAL SCATTERING},
Abstract = {We show that classical chaotic scattering has experimentally
measurable consequences for the quantum conductance of
semiconductor microstructures. These include the existence
of conductance fluctuations-a sensitivity of the conductance
to either Fermi energy or magnetic field-and
weak-localization-a change in the average conductance upon
applying a magnetic field. We develop a semiclassical theory
and present numerical results for these two effects in which
we model the microstructures by billiards attached to leads.
We find that the difference between chaotic and regular
classical scattering produces a qualitative difference in
the fluctuation spectrum and weak-localization lineshape of
chaotic and nonchaotic structures. While the semiclassical
theory within the diagonal approximation accounts well for
the weak-localization lineshape and for the spectrum of the
fluctuations, we uncover a surprising failure of the
semiclassical diagonal-approximation theory in describing
the magnitude of these quantum transport
effects.},
Doi = {10.1063/1.165928},
Key = {baranger:665}
}
@booklet{Nockel93,
Author = {J. U. Nockel and A. D. Stone and H. U. Baranger},
Title = {Adiabatic turn-on and the asymptotic limit in
linear-response theory for open systems},
Journal = {Physical Review B},
Volume = {48},
Number = {23},
Pages = {17569 -- 17572},
Year = {1993},
Month = {December},
Key = {Nockel93}
}
@article{nockel:17569,
Author = {Nöckel, JU and Stone, AD and Baranger, HU},
Title = {Adiabatic turn-on and the asymptotic limit in
linear-response theory for open systems.},
Journal = {Physical review. B, Condensed matter},
Volume = {48},
Number = {23},
Pages = {17569-17572},
Publisher = {APS},
Year = {1993},
Month = {December},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/10008374},
Keywords = {TRANSPORT THEORY; KUBO FORMULA; ADIABATIC PROCESSES;
MATHEMATICAL MODELS; ELECTRIC CONDUCTIVITY;
SCATTERING},
Doi = {10.1103/physrevb.48.17569},
Key = {nockel:17569}
}
@article{baranger:142,
Author = {Baranger, HU and Mello, PA},
Title = {Mesoscopic transport through chaotic cavities: A random
S-matrix theory approach.},
Journal = {Physical review letters},
Volume = {73},
Number = {1},
Pages = {142-145},
Publisher = {APS},
Year = {1994},
Month = {July},
url = {http://www.ncbi.nlm.nih.gov/pubmed/10056740},
Keywords = {S MATRIX; TRANSPORT THEORY; MICROSTRUCTURE; NANOSTRUCTURES;
CHAOTIC SYSTEMS; SCATTERING THEORY; INTERFERENCE;
FLUCTUATIONS; MAGNETIC FIELD EFFECTS},
Doi = {10.1103/physrevlett.73.142},
Key = {baranger:142}
}
@article{hastings:8230,
Author = {Hastings, MB and Stone, AD and Baranger, HU},
Title = {Inequivalence of weak localization and coherent
backscattering.},
Journal = {Physical review. B, Condensed matter},
Volume = {50},
Number = {12},
Pages = {8230-8244},
Publisher = {APS},
Year = {1994},
Month = {September},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/9974840},
Keywords = {COHERENT SCATTERING; BACKSCATTERING; DISORDERED SYSTEMS;
ELECTRIC CONDUCTIVITY; LOCALIZED STATES; CHAOTIC SYSTEMS;
REFLECTION; BALLISTICS; SYMMETRY; ELECTRIC
CONDUCTORS},
Doi = {10.1103/physrevb.50.8230},
Key = {hastings:8230}
}
@booklet{Chang94,
Author = {A. M. Chang and H. U. Baranger and L. N. Pfeiffer and K. W.
West},
Title = {Weak-localization in chaotic versus nonchaotic cavities - a
striking difference in the line-shape},
Journal = {Physical Review Letters},
Volume = {73},
Number = {15},
Pages = {2111 -- 2114},
Year = {1994},
Month = {October},
Key = {Chang94}
}
@article{chang:2111,
Author = {Chang, AM and Baranger, HU and Pfeiffer, LN and West,
KW},
Title = {Weak localization in chaotic versus nonchaotic cavities: A
striking difference in the line shape.},
Journal = {Physical review letters},
Volume = {73},
Number = {15},
Pages = {2111-2114},
Publisher = {APS},
Year = {1994},
Month = {October},
url = {http://www.ncbi.nlm.nih.gov/pubmed/10056974},
Keywords = {TRANSPORT PROCESSES; CHAOTIC SYSTEMS; SCATTERING; CAVITY
RESONATORS; MAGNETORESISTANCE; AHARONOV – BOHM EFFECT;
QUANTUM WELLS; COHERENCE LENGTH},
Doi = {10.1103/physrevlett.73.2111},
Key = {chang:2111}
}
@article{fds340702,
Author = {Mello, PA and Baranger, HU},
Title = {Electronic transport through ballistic chaotic cavities: an
information theoretic approach},
Volume = {220},
Number = {1},
Pages = {15-23},
Year = {1995},
Abstract = {The statistical properties of the electronic conductance
through a ballistic quantum dot are studied by means of an
information-theoretic statistical model for the scattering
matrix. The model, introduced in the past in the context of
nuclear physics, describes the problem in terms of a prompt
and an equilibrated component: it incorporates the average
value of the scattering matrix to describe the prompt
processes and satisfies the requirements of flux
conservation, causality and ergodicity. The model describes
well the results arising from the numerical solution of the
Schrödinger equation for two-dimensional quantum
cavities.},
Key = {fds340702}
}
@article{sumetskii:1352,
Author = {Sumetskii, MI and Baranger, HU},
Title = {Studying the insulator-conductor interface with a scanning
tunneling microscope},
Journal = {Applied Physics Letters},
Volume = {66},
Number = {11},
Pages = {1352},
Publisher = {AIP Publishing},
Year = {1995},
Month = {January},
ISSN = {0003-6951},
url = {http://link.aip.org/link/?APL/66/1352/1},
Keywords = {SILICON; SILICON OXIDES; INTERFACE STRUCTURE; STM;
MORPHOLOGY; SPATIAL RESOLUTION; ROUGHNESS},
Abstract = {We suggest that a scanning tunneling microscope (STM) may be
used for investigating the insulator-conductor interface, in
particular SiO2/Si, at nanometer scale. For an insulating
film transparent to tunneling, we estimate, using a simple
model, the roughness of the interface from the STM image. It
is found that the interface roughness is less than the
roughness of the image surface times the ratio of effective
decay lengths in the film and in vacuum. For relatively wide
films, of order 10 nm, STM measurement in the field emission
regime can give the interface image with 1 nm precision.©
1995 American Institute of Physics.},
Doi = {10.1063/1.113198},
Key = {sumetskii:1352}
}
@booklet{Baranger95a,
Author = {Baranger, HU and Mello, PA},
Title = {Effect of phase breaking on quantum transport through
chaotic cavities.},
Journal = {Physical review. B, Condensed matter},
Volume = {51},
Number = {7},
Pages = {4703-4706},
Publisher = {APS},
Year = {1995},
Month = {February},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/9979331},
Keywords = {CHAOTIC SYSTEMS; CAVITIES; QUANTUM DOTS; TRANSPORT
PROCESSES; INTERFERENCE; PHASE SHIFT; S MATRIX; ANALYTICAL
SOLUTION},
Doi = {10.1103/physrevb.51.4703},
Key = {Baranger95a}
}
@article{fds362605,
Author = {Baranger, HU and Mello, PA},
Title = {SCATTERING INVOLVING PROMPT AND EQUILIBRATED COMPONENTS,
INFORMATION THEORY, AND CHAOTIC QUANTUM DOTS},
Year = {1995},
Month = {February},
Abstract = {We propose an information-theoretic statistical model to
describe the universal features of those chaotic scattering
processes characterized by a prompt and an equilibrated
component. The model, introduced in the past in nuclear
physics, incorporates the average value of the scattering
matrix to describe the prompt processes, and satisfies the
requirements of flux conservation, causality, and
ergodicity. We show that the model successfully describes
electronic transport through chaotic quantum dots. The
predicted distribution of the conductance may show a
remarkable two-peak structure.},
Key = {fds362605}
}
@booklet{Aleiner95,
Author = {Aleiner, IL and Baranger, HU and Glazman, LI},
Title = {Tunneling into a Two-Dimensional Electron Liquid in a Weak
Magnetic Field.},
Journal = {Physical review letters},
Volume = {74},
Number = {17},
Pages = {3435-3438},
Year = {1995},
Month = {April},
url = {http://www.ncbi.nlm.nih.gov/pubmed/10058200},
Doi = {10.1103/physrevlett.74.3435},
Key = {Aleiner95}
}
@booklet{Baranger95,
Author = {Baranger, HU},
Title = {Quantum transport and chaos in semiconductor
microstructures},
Journal = {Physica D: Nonlinear Phenomena},
Volume = {83},
Number = {1-3},
Pages = {30-45},
Publisher = {Elsevier BV},
Year = {1995},
Month = {May},
ISSN = {0167-2789},
url = {http://dx.doi.org/10.1016/0167-2789(94)00248-O},
Abstract = {It is shown that classical chaotic scattering has
experimentally measurable consequences for the quantum
conductance of semiconductor microstructures. These include
the existence of conductance fluctuations -a sensitivity of
the conductance to either Fermi energy or magnetic field-
and weak-localization -a change in the average conductance
upon applying a magnetic field. We use semiclassical theory,
random S-matrix theory, and numerical results to describe
these interference effects for microstructures modeled by
billiards attached to leads. The semiclassical theory
predicts that the difference between chaotic and regular
classical scattering produces a qualitative difference in
the fluctuation spectrum and weak-localization lineshape of
chaotic versus non-chaotic structures. The random S-matrix
theory yields results for the magnitude of these
interference effects. The conductance fluctuation and
weak-localization magnitudes are universal if the number of
incoming modes, N, is large: they are independent of the
size and shape of the cavity. Of more relevance
experimentally, in the limit of small N the full
distribution of the conductance shows a striking dependence
on N and magnetic field. © 1995.},
Doi = {10.1016/0167-2789(94)00248-O},
Key = {Baranger95}
}
@booklet{Mello95,
Author = {Mello, PA and Baranger, HU},
Title = {Electronic transport through ballistic chaotic cavities: an
information theoretic approach},
Journal = {Physica A: Statistical Mechanics and its
Applications},
Volume = {220},
Number = {1-2},
Pages = {15-23},
Publisher = {Elsevier BV},
Year = {1995},
Month = {October},
ISSN = {0378-4371},
url = {http://dx.doi.org/10.1016/0378-4371(95)00121-M},
Abstract = {The statistical properties of the electronic conductance
through a ballistic quantum dot are studied by means of an
information-theoretic statistical model for the scattering
matrix. The model, introduced in the past in the context of
nuclear physics, describes the problem in terms of a prompt
and an equilibrated component: it incorporates the average
value of the scattering matrix to describe the prompt
processes and satisfies the requirements of flux
conservation, causality and ergodicity. The model describes
well the results arising from the numerical solution of the
Schrödinger equation for two-dimensional quantum cavities.
© 1995.},
Doi = {10.1016/0378-4371(95)00121-M},
Key = {Mello95}
}
@booklet{Sumetskii95,
Author = {Sumetskii, MI and Baranger, HU},
Title = {Change in sign of the photocurrent in a coherent asymmetric
superlattice},
Journal = {Applied Physics Letters},
Volume = {67},
Number = {24},
Pages = {3560},
Publisher = {AIP Publishing},
Year = {1995},
Month = {December},
url = {http://link.aip.org/link/?APL/67/3560/1},
Keywords = {FREQUENCY DEPENDENCE; INTERFERENCE; OSCILLATIONS;
PHOTOCONDUCTIVITY; PHOTOCURRENTS; QUANTUM WELLS;
SUPERLATTICES},
Abstract = {We study the photocurrent induced in an asymmetric
superlattice as a function of the frequency of applied
radiation. In order to investigate the principal features,
we consider the simplest finite-period structure: one
containing an asymmetric unit formed of two narrow quantum
wells. It is found that the main features of the
photocurrent-frequency curve are insensitive to the number
of periods. Considering a single-unit structure, we find
simple equations for the photocurrent reversal points. The
oscillations in sign of the photocurrent are shown to result
from quantum interference of the electron waves reflected at
the interfaces in the structure. Using our model, we
approximate an experimental structure and explain the
observed photocurrent reversal.© 1995 American Institute of
Physics.},
Doi = {10.1063/1.114921},
Key = {Sumetskii95}
}
@article{matveev:1034,
Author = {Matveev, KA and Glazman, LI and Baranger, HU},
Title = {Tunneling spectroscopy of quantum charge fluctuations in the
Coulomb blockade.},
Journal = {Physical review. B, Condensed matter},
Volume = {53},
Number = {3},
Pages = {1034-1037},
Publisher = {APS},
Year = {1996},
Month = {January},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/9983548},
Keywords = {COULOMB EXCITATION; ELECTRIC CONDUCTIVITY; ELECTRONIC
STRUCTURE; FLUCTUATIONS; GROUND STATES; TEMPERATURE
DEPENDENCE; TUNNEL EFFECT; ELECTRON CHARGE; QUANTUM
DOTS},
Doi = {10.1103/physrevb.53.1034},
Key = {matveev:1034}
}
@booklet{Baranger96a,
Author = {Baranger, HU and Mello, PA},
Title = {Short paths and information theory in quantum chaotic
scattering: Transport through quantum dots},
Journal = {Europhysics Letters},
Volume = {33},
Number = {6},
Pages = {465-470},
Publisher = {IOP Publishing},
Year = {1996},
Month = {February},
ISSN = {0295-5075},
url = {http://dx.doi.org/10.1209/epl/i1996-00364-5},
Abstract = {We propose an information-theoretic model to describe the
common features of typical chaotic scattering processes by
including two time scales, a prompt and an equilibrated
component. The model, introduced in nuclear physics, uses
the average value of the scattering matrix to describe the
prompt processes, and satisfies flux conservation,
causality, and ergodicity. We show that the model
successfully describes electronic transport through a much
larger class of chaotic quantum dots than previously
considered. The predicted distribution of the conductance
may differ dramatically from that of previous
models.},
Doi = {10.1209/epl/i1996-00364-5},
Key = {Baranger96a}
}
@booklet{Chang96,
Author = {A. M. Chang and H. U. Baranger and L. N. Pfeiffer and K. W. West and T. Y. Chang},
Title = {Non-Gaussian distribution of Coulomb blockade peak heights
in quantum dots},
Journal = {Phys. Rev. Lett.},
Volume = {76},
Number = {10},
Pages = {1695 -- 1698},
Year = {1996},
Month = {March},
Key = {Chang96}
}
@article{chang:1695,
Author = {Chang, AM and Baranger, HU and Pfeiffer, LN and West, KW and Chang,
TY},
Title = {Non-Gaussian distribution of Coulomb blockade peak heights
in quantum dots.},
Journal = {Physical review letters},
Volume = {76},
Number = {10},
Pages = {1695-1698},
Publisher = {APS},
Year = {1996},
Month = {March},
url = {http://www.ncbi.nlm.nih.gov/pubmed/10060494},
Keywords = {QUANTUM DOTS; TUNNELING; IV CHARACTERISTIC; COULOMB FIELD;
GALLIUM ARSENIDES; ALUMINIUM ARSENIDES},
Doi = {10.1103/physrevlett.76.1695},
Key = {chang:1695}
}
@booklet{Matveev96a,
Author = {Matveev, KA and Glazman, LI and Baranger, HU},
Title = {Theory of Coulomb blockade of tunneling through a double
quantum dot},
Journal = {Surface Science},
Volume = {361-362},
Number = {1-3},
Pages = {623-626},
Publisher = {Elsevier BV},
Year = {1996},
Month = {July},
url = {http://dx.doi.org/10.1016/0039-6028(96)00484-0},
Abstract = {We present a theory of Coulomb blockade oscillations in
tunneling through a pair of quantum dots connected by a
tunable tunneling junction. The positions and amplitudes of
peaks in the linear conductance are directly related,
respectively, to the ground state energy and to the dynamics
of charge fluctuations. Our theory allows for a quantitative
comparison with the experimentally observed peak positions.
In the strong tunneling limit, we predict a striking
powder-law temperature-dependence of the peak
amplitudes.},
Doi = {10.1016/0039-6028(96)00484-0},
Key = {Matveev96a}
}
@booklet{Matveev96,
Author = {K. A. Matveev and L. I. Glazman and H. U. Baranger},
Title = {Coulomb blockade of tunneling through a double quantum
dot},
Journal = {Physical Review B},
Volume = {54},
Number = {8},
Pages = {5637 -- 5646},
Year = {1996},
Month = {August},
Key = {Matveev96}
}
@article{matveev:5637,
Author = {Matveev, KA and Glazman, LI and Baranger, HU},
Title = {Coulomb blockade of tunneling through a double quantum
dot.},
Journal = {Physical review. B, Condensed matter},
Volume = {54},
Number = {8},
Pages = {5637-5646},
Publisher = {APS},
Year = {1996},
Month = {August},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/9986527},
Keywords = {TUNNEL EFFECT; COULOMB FIELD; ELECTRIC CONDUCTIVITY;
TEMPERATURE DEPENDENCE; FLUCTUATIONS; PEAKS; QUANTUM
DOTS},
Doi = {10.1103/physrevb.54.5637},
Key = {matveev:5637}
}
@booklet{Baranger96,
Author = {Baranger, HU and Mello, PA},
Title = {Reflection symmetric ballistic microstructures: Quantum
transport properties.},
Journal = {Physical review. B, Condensed matter},
Volume = {54},
Number = {20},
Pages = {R14297-R14300},
Publisher = {APS},
Year = {1996},
Month = {November},
ISSN = {0163-1829},
url = {http://www.ncbi.nlm.nih.gov/pubmed/9985511},
Keywords = {NANOSTRUCTURES; CHAOTIC SYSTEMS; HETEROSTRUCTURES; TRANSPORT
PROCESSES; ELECTRIC CONDUCTIVITY; TRANSMISSION; S MATRIX;
REFLECTION; P INVARIANCE},
Doi = {10.1103/physrevb.54.r14297},
Key = {Baranger96}
}
@booklet{Gopar96,
Author = {Gopar, VA and Martínez, M and Mello, PA and Baranger,
HU},
Title = {The invariant measure for scattering matrices with block
symmetries},
Journal = {Journal of Physics A: Mathematical and General},
Volume = {29},
Number = {4},
Pages = {881-888},
Publisher = {IOP Publishing},
Year = {1996},
Month = {December},
ISSN = {0305-4470},
url = {http://dx.doi.org/10.1088/0305-4470/29/4/014},
Abstract = {We find the invariant measure for two new types of S
matrices relevant for chaotic scattering from a cavity in a
waveguide. The S matrices considered can be written as a 2
× 2 matrix of blocks, each of rank N, in which the two
diagonal blocks are identical and the two off-diagonal
blocks are identical. The S matrices are unitary; in
addition, they may be symmetric because of time-reversal
symmetry. The invariant measure, with and without the
condition of symmetry, is given explicitly in terms of the
invariant measures for the well known circular unitary and
orthogonal ensembles. Some implications are drawn for the
resulting statistical distribution of the transmission
coefficient through a chaotic cavity. © 1996 IOP Publishing
Ltd.},
Doi = {10.1088/0305-4470/29/4/014},
Key = {Gopar96}
}
@booklet{Hasen97,
Author = {Hasen, J and Pfeiffer, LN and Pinczuk, A and Baranger, HU and West, KW and Dennis, BS},
Title = {Large excitonic confinement in asymmetric quantum T
wires},
Journal = {Superlattices and Microstructures},
Volume = {22},
Number = {3},
Pages = {359-364},
Publisher = {Elsevier BV},
Year = {1997},
Month = {January},
url = {http://dx.doi.org/10.1006/spmi.1996.0283},
Abstract = {An asymmetric quantum T wire (QTWR) may be formed whenever
two quantum wells (QW) of differing widths intersect. We
measured the photoluminescence and photoluminescence
excitation from such QTWRs using microscope optics with high
spatial resolution. The introduction of an asymmetry in the
design of the QWs allows us to compensate for the different
effective masses of the heavy holes in the (100) and (110)
directions. We find that the confinement energy for excitons
in the asymmetric QTWR is 40 meV, which is greater than
previously published reports on symmetric QTWRs.
Consequently, the confinement energy exceeds kT at room
temperature, which appeals to device applications.
Furthermore, the confinement energy is greater than the LO
phonon energy, a feature which may improve the capture rate
of the QTWR and decrease the escape rate at higher
temperatures. Finally, using the results from calculations,
we estimate the binding energy of the exciton to be about 20
meV, which is substantially larger than the binding energy
in QWs. This result agrees with theoretical predictions of
an increase in exciton binding energy in ID confinement. ©
1997 Academic Press Limited.},
Doi = {10.1006/spmi.1996.0283},
Key = {Hasen97}
}
@article{fds245170,
Author = {Ullmo, D and Richter, K and Baranger, HU and Von Oppen and F and Jalabert,
RA},
Title = {Semiclassical approach to orbital magnetism of interacting
diffusive quantum systems},
Journal = {Physica E: Low-Dimensional Systems and Nanostructures},
Volume = {1},
Number = {1-4},
Pages = {268-273},
Publisher = {Elsevier BV},
Year = {1997},
Month = {January},
url = {http://dx.doi.org/10.1016/s1386-9477(97)00058-1},
Abstract = {We study interaction effects on the orbital magnetism of
diffusive mesoscopic quantum systems. By combining many-body
perturbation theory with semiclassical techniques, we show
that the interaction contribution to the ensemble-averaged
quantum thermodynamic potential can be reduced to an
essentially classical operator. We compute the magnetic
response of disordered rings and dots for diffusive
classical dynamics. Our semiclassical approach reproduces
the results of previous diagrammatic quantum calculations.
© 1997 Elsevier Science B.V. All rights
reserved.},
Doi = {10.1016/s1386-9477(97)00058-1},
Key = {fds245170}
}
@booklet{Ullmo97,
Author = {D. Ullmo and K. Richter and H. U. Baranger and F. von Oppen and R. A. Jalabert},
Title = {Semiclassical approach to orbital magnetism of interacting
diffusive quantum systems},
Journal = {Physica E},
Volume = {1},
Number = {1-4},
Pages = {268 -- 273},
Year = {1997},
Month = {December},
Key = {Ullmo97}
}
@booklet{Ullmo98,
Author = {Ullmo, D and Baranger, HU and Richter, K and Von Oppen and F and Jalabert,
RA},
Title = {Chaos and interacting electrons in ballistic quantum
dots},
Journal = {Physical Review Letters},
Volume = {80},
Number = {5},
Pages = {895-899},
Publisher = {American Physical Society (APS)},
Year = {1998},
Month = {January},
url = {http://dx.doi.org/10.1103/PhysRevLett.80.895},
Abstract = {We show that the classical dynamics of independent particles
can determine the quantum properties of interacting
electrons in the ballistic regime. This connection is
established using diagrammatic perturbation theory and
semiclassical finite-temperature Green functions.
Specifically, the orbital magnetism is greatly enhanced by
the combined effects of interactions and finite size. The
presence of families of periodic orbits in regular systems
makes their susceptibility parametrically larger than that
of chaotic systems, a difference which emerges from
correlation terms. © 1998 American Physical
Society.},
Doi = {10.1103/PhysRevLett.80.895},
Key = {Ullmo98}
}
@article{fds245051,
Author = {Narimanov, EE and Cerruti, NR and Baranger, HU and Tomsovic,
S},
Title = {Anomalous low temperature behavior of superconducting
Nd1.85Ce0.15CuO4-y},
Journal = {Physical Review Letters},
Volume = {83},
Number = {13},
Pages = {2644-2647},
Year = {1999},
ISSN = {0031-9007},
Abstract = {Bicrystal grain boundary Josephson junctions of the
electron-doped cuprate superconductor Nd1.85Ce0.15CuO4-y are
used to measure the temperature dependence of the in-plane
London penetration depth λab(T) and the maximum Josephson
current Ic(T). Results showed that λab(T) and Ic(T)
anomalously increases and decreases, respectively, with
decreasing temperature below 4 K due to the presence of the
Nd3+ paramagnetic moments.},
Key = {fds245051}
}
@article{fds4755,
Author = {H. U. Baranger and R. M. Westervelt},
Title = {Chaos in Ballistic Nanostructures},
Pages = {537-628},
Booktitle = {Nanotechnology},
Publisher = {Springer-Verlag},
Editor = {G. Timp},
Year = {1999},
Key = {fds4755}
}
@booklet{Ullmo99,
Author = {Ullmo, D and Baranger, HU},
Title = {Wireless propagation in buildings: a statistical scattering
approach},
Journal = {IEEE Transactions on Vehicular Technology},
Volume = {48},
Number = {3},
Pages = {947-955},
Publisher = {Institute of Electrical and Electronics Engineers
(IEEE)},
Year = {1999},
Month = {January},
ISSN = {0018-9545},
url = {http://dx.doi.org/10.1109/25.765025},
Abstract = {A new approach to the modeling of wireless propagation in
buildings is introduced. We treat the scattering by walls
and local clutter probabilistically through either a
relaxation-time approximation in a Boltzmann equation or by
using a diffusion equation. The result is a range of models
in which one can vary the tradeoff between the complexity of
the building description and the accuracy of the prediction.
The two limits of this range are ray tracing at the most
accurate end and a simple decay law at the most simple. By
comparing results for two of these new models with
measurements, we conclude that a reasonably accurate
description of propagation can be obtained with a relatively
simple model. The most effective way to use the models is by
combining them with a few measurements through a sampling
technique.},
Doi = {10.1109/25.765025},
Key = {Ullmo99}
}
@article{fds245192,
Author = {Narimanov, EE and Cerruti, NR and Baranger, HU and Tomsovic,
S},
Title = {Chaos in quantum dots: Dynamical modulation of coulomb
blockade peak heights},
Journal = {Physical Review Letters},
Volume = {83},
Number = {13},
Pages = {2640-2643},
Publisher = {American Physical Society (APS)},
Year = {1999},
Month = {January},
ISSN = {0031-9007},
url = {http://dx.doi.org/10.1103/PhysRevLett.83.2640},
Abstract = {We develop a semiclassical theory of Coulomb blockade peak
heights in quantum dots and show that the dynamics in the
dot leads to a large modulation of the peak height. The
corrections to the standard statistical theory of peak
height distributions, power spectra, and correlation
functions are nonuniversal and can be expressed in terms of
the classical periodic orbits of the dot that are well
coupled to the leads. The resulting correlation function
oscillates as a function of the peak number in a way defined
by such orbits. In addition, the correlation of adjacent
conductance peaks is enhanced. Both of these effects are in
agreement with recent experiments. © 1999 The American
Physical Society.},
Doi = {10.1103/PhysRevLett.83.2640},
Key = {fds245192}
}
@article{fds360505,
Author = {Mello, PA and Baranger, HU},
Title = {Interference phenomena in electronic transport through
chaotic cavities: An information-theoretic
approach},
Journal = {LATIN-AMERICAN SCHOOL OF PHYSICS XXXI ELAF},
Volume = {464},
Pages = {281-333},
Publisher = {AMER INST PHYSICS},
Editor = {Hacyan, S and Jauregui, R and LopezPena, R},
Year = {1999},
Month = {January},
Key = {fds360505}
}
@booklet{Narimanov99,
Author = {E. E. Narimanov and N. R. Cerruti and H. U. Baranger and S.
Tomsovic},
Title = {Chaos in quantum dots: Dynamical modulation of Coulomb
blockade peak heights},
Journal = {Physical Review Letters},
Volume = {83},
Number = {13},
Pages = {2640 -- 2643},
Year = {1999},
Month = {September},
Key = {Narimanov99}
}
@booklet{Moustakas00,
Author = {A. L. Moustakas and H. U. Baranger and L. Balents and A. M. Sengupta and S. H. Simon},
Title = {Communication through a diffusive medium: Coherence and
capacity},
Journal = {Science},
Volume = {287},
Number = {5451},
Pages = {287 -- 290},
Year = {2000},
Month = {January},
Key = {Moustakas00}
}
@article{fds245191,
Author = {Moustakas, AL and Baranger, HU and Balents, L and Sengupta, AM and Simon, SH},
Title = {Communication through a diffusive medium: coherence and
capacity},
Journal = {Science (New York, N.Y.)},
Volume = {287},
Number = {5451},
Pages = {287-290},
Year = {2000},
Month = {January},
url = {http://www.ncbi.nlm.nih.gov/pubmed/10634779},
Abstract = {Coherent wave propagation in disordered media gives rise to
many fascinating phenomena as diverse as universal
conductance fluctuations in mesoscopic metals and speckle
patterns in light scattering. Here, the theory of
electromagnetic wave propagation in diffusive media is
combined with information theory to show how interference
affects the information transmission rate between antenna
arrays. Nontrivial dependencies of the information capacity
on the nature of the antenna arrays are found, such as the
dimensionality of the arrays and their direction with
respect to the local scattering medium. This approach
provides a physical picture for understanding the importance
of scattering in the transfer of information through
wireless communications.},
Doi = {10.1126/science.287.5451.287},
Key = {fds245191}
}
@booklet{Baranger00,
Author = {Baranger, HU and Ullmo, D},
Title = {Interactions and interference in quantum dots: Kinks in
Coulomb-blockade peak positions},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {61},
Number = {4},
Pages = {R2425-R2428},
Publisher = {American Physical Society (APS)},
Year = {2000},
Month = {January},
ISSN = {0163-1829},
url = {http://dx.doi.org/10.1103/PhysRevB.61.R2425},
Abstract = {We investigate the spin of the ground state of a
geometrically confined many-electron system. For atoms,
shell structure simplifies this problem—the spin is
prescribed by the well-known Hund’s rule. In contrast,
quantum dots provide a controllable setting for studying the
interplay of quantum interference and electron-electron
interactions in general cases. In a generic confining
potential, the shell-structure argument suggests a singlet
ground state for an even number of electrons. The
interaction among the electrons produces, however,
accidental occurrences of spin-triplet ground states, even
for weak interaction, a limit which we analyze explicitly.
Variation of an external parameter causes sudden switching
between these states and hence a kink in the conductance.
Experimental study of these kinks would yield the exchange
energy for the “chaotic electron gas”. © 2000 The
American Physical Society.},
Doi = {10.1103/PhysRevB.61.R2425},
Key = {Baranger00}
}
@booklet{Oppen00,
Author = {von Oppen, F and Ullmo, D and Baranger, HU},
Title = {Interaction-induced magnetization of a two-dimensional
electron gas},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {62},
Number = {3},
Pages = {1935-1942},
Publisher = {American Physical Society (APS)},
Year = {2000},
Month = {January},
ISSN = {0163-1829},
url = {http://dx.doi.org/10.1103/PhysRevB.62.1935},
Abstract = {We consider the contribution of electron-electron
interactions to the orbital magnetization of a
two-dimensional electron gas, focusing on the ballistic
limit in the regime of negligible Landau-level spacing. This
regime can be described by combining diagrammatic
perturbation theory with semiclassical techniques. At
sufficiently low temperatures, the interaction-induced
magnetization overwhelms the Landau and Pauli contributions.
Curiously, the interaction-induced magnetization is
third-order in the (renormalized) Coulomb interaction. We
give a simple interpretation of this effect in terms of
classical paths using a renormalization argument: a polygon
must have at least three sides in order to enclose an area.
To leading order in the renormalized interaction, the
renormalization argument gives exactly the same result as
the full treatment. © 2000 The American Physical
Society.},
Doi = {10.1103/PhysRevB.62.1935},
Key = {Oppen00}
}
@booklet{Usaj01a,
Author = {Usaj, G and Baranger, HU},
Title = {Mesoscopic tunneling magnetoresistance},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {63},
Number = {18},
Pages = {1844181-1844185},
Year = {2001},
ISSN = {0163-1829},
url = {http://arxiv.org/abs/cond-mat/0006429v3},
Abstract = {We study spin-dependent transport through
ferromagnet/normal-metal/ferromagnet double tunnel junctions
in the mesoscopic Coulomb-blockade regime. We calculate the
conductance in the absence or presence of spin-orbit
interaction and for arbitrary orientation of the lead
magnetizations. The tunneling magnetoresistance (TMR),
defined at the Coulomb-blockade conductance peaks, is
calculated and its probability distribution presented. We
show that mesoscopic fluctuations can lead to the optimal
value of the TMR and that the conductance in noncollinear
configurations gives information about how the spin rotates
inside the grain.},
Doi = {10.1103/PhysRevB.63.184418},
Key = {Usaj01a}
}
@booklet{Ullmo01a,
Author = {Ullmo, D and Nagano, T and Tomsovic, S and Baranger,
HU},
Title = {Semiclassical density functional theory: Strutinsky energy
corrections in quantum dots},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {63},
Number = {12},
Pages = {1253391-12533913},
Year = {2001},
ISSN = {0163-1829},
Abstract = {We develop a semiclassical density functional theory in the
context of quantum dots. Coulomb blockade conductance
oscillations have been measured in several experiments using
nanostructured quantum dots. The statistical properties of
these oscillations remain puzzling, however, particularly
the statistics of spacings between conductance peaks. To
explore the role that residual interactions may play in the
spacing statistics, we consider many-body systems that
include electron-electron interactions through an explicit
density functional. First, we develop an approximate series
expansion for obtaining the ground state using the idea of
the Strutinsky shell correction method. Next, we relate the
second-order semiclassical corrections to the screened
Coulomb potential. Finally, we investigate the validity of
the approximation method by numerical calculation of a
one-dimensional model system, and show the relative
magnitudes of the successive terms as a function of particle
number.},
Key = {Ullmo01a}
}
@booklet{Mathur01,
Author = {Mathur, H and Baranger, HU},
Title = {Random berry phase magnetoresistance as a probe of interface
roughness in Si MOSFET'S},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {64},
Number = {23},
Pages = {2353251-23532520},
Year = {2001},
ISSN = {0163-1829},
Abstract = {The effect of silicon-oxide interface roughness on the
weak-localization magnetoconductance of a silicon
metal-oxide-semiconductor field-effect transistor in a
magnetic field, tilted with respect to the interface, is
studied. It is shown that an electron picks up a random
Berry's phase as it traverses a closed orbit. Effectively,
due to roughness, the electron sees a uniform field parallel
to the interface as a random perpendicular field. At zero
parallel field the dependence of the conductance on the
perpendicular field has a well-known form, the
weak-localization line shape. Here the effect of applying a
fixed parallel field on the line shape is analyzed. Many
types of behavior are found including homogeneous
broadening, inhomogeneous broadening, and a remarkable
regime in which the change in line shape depends only on the
magnetic field, the two length scales that characterize the
interface roughness, and fundamental constants. Good
agreement is obtained with experiments that are in the
homogeneous broadening limit. The implications for using
weak-localization magneto-conductance as a probe of
interface roughness, as proposed by Wheeler and co-workers,
are discussed.},
Key = {Mathur01}
}
@article{fds303610,
Author = {Usaj, G and Baranger, HU},
Title = {Coulomb-blockade peak-spacing distribution: Interplay of
temperature and spin},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {64},
Number = {20},
Pages = {2013191-2013194},
Publisher = {American Physical Society (APS)},
Year = {2001},
ISSN = {0163-1829},
url = {http://arxiv.org/abs/cond-mat/0108027v1},
Abstract = {We calculate the Coulomb-blockade peak-spacing distribution
at finite temperature using the recently introduced
"universal Hamiltonian" to describe the e-e interactions. We
show that the temperature effect is important even at
kBT∼Δ (Δ is the single-particle mean level spacing).
This sensitivity arises because: 1) exchange reduces the
minimum energy of excitation from the ground state, and 2)
the entropic contribution depends on the change of the spin
of the quantum dot. Including the leading corrections to the
universal Hamiltonian yields results in quantitative
agreement with the experiments. Surprisingly, temperature
appears to be the most important effect.},
Doi = {10.1103/PhysRevB.64.201319},
Key = {fds303610}
}
@article{fds303609,
Author = {Mathur, H and Baranger, HU},
Title = {Random Berry phase magnetoresistance as a probe of interface
roughness in Si MOSFET’s},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {64},
Number = {23},
Pages = {235325},
Publisher = {American Physical Society (APS)},
Year = {2001},
Month = {January},
url = {http://arxiv.org/abs/cond-mat/0008375v1},
Abstract = {The effect of silicon-oxide interface roughness on the
weak-localization magnetoconductance of a silicon
metal-oxide-semiconductor field-effect transistor in a
magnetic field, tilted with respect to the interface, is
studied. It is shown that an electron picks up a random
Berry’s phase as it traverses a closed orbit. Effectively,
due to roughness, the electron sees a uniform field parallel
to the interface as a random perpendicular field. At zero
parallel field the dependence of the conductance on the
perpendicular field has a well-known form, the
weak-localization line shape. Here the effect of applying a
fixed parallel field on the line shape is analyzed. Many
types of behavior are found including homogeneous
broadening, inhomogeneous broadening, and a remarkable
regime in which the change in line shape depends only on the
magnetic field, the two length scales that characterize the
interface roughness, and fundamental constants. Good
agreement is obtained with experiments that are in the
homogeneous broadening limit. The implications for using
weak-localization magnetoconductance as a probe of interface
roughness, as proposed by Wheeler and co-workers, are
discussed. © 2001 The American Physical
Society.},
Doi = {10.1103/PhysRevB.64.235325},
Key = {fds303609}
}
@article{fds330533,
Author = {Usaj, G and Baranger, HU},
Title = {TMR in nanoscale F-N-F systems: Mesoscopic
fluctuations},
Journal = {Electronic Correlations: From Meso- to Nano-Physics},
Pages = {493-496},
Publisher = {E D P SCIENCES},
Editor = {Martin, T and Montambaux, G and ThanhVan, JT},
Year = {2001},
Month = {January},
ISBN = {2-86883-570-8},
Key = {fds330533}
}
@article{fds303611,
Author = {Ullmo, D and Nagano, T and Tomsovic, S and Baranger,
HU},
Title = {Semiclassical density functional theory: Strutinsky energy
corrections in quantum dots},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {63},
Number = {12},
Pages = {125339},
Publisher = {American Physical Society (APS)},
Year = {2001},
Month = {March},
url = {http://arxiv.org/abs/cond-mat/0007330v1},
Abstract = {We develop a semiclassical density functional theory in the
context of quantum dots. Coulomb blockade conductance
oscillations have been measured in several experiments using
nanostructured quantum dots. The statistical properties of
these oscillations remain puzzling, however, particularly
the statistics of spacings between conductance peaks. To
explore the role that residual interactions may play in the
spacing statistics, we consider many-body systems that
include electron-electron interactions through an explicit
density functional. First, we develop an approximate series
expansion for obtaining the ground state using the idea of
the Strutinsky shell correction method. Next, we relate the
second-order semiclassical corrections to the screened
Coulomb potential. Finally, we investigate the validity of
the approximation method by numerical calculation of a
one-dimensional model system, and show the relative
magnitudes of the successive terms as a function of particle
number. © 2001 The American Physical Society.},
Doi = {10.1103/PhysRevB.63.125339},
Key = {fds303611}
}
@booklet{Usaj01,
Author = {Usaj, G and Baranger, HU},
Title = {Coulomb-blockade peak-spacing distribution: Interplay of
temperature and spin},
Journal = {Physical Review B},
Volume = {6420},
Number = {20},
Pages = {art. no.-201319},
Year = {2001},
Month = {November},
ISSN = {0163-1829},
Abstract = {We calculate the Coulomb-blockade peak-spacing distribution
at finite temperature using the recently introduced
"universal Hamiltonian" to describe the e-e interactions. We
show that the temperature effect is important even at
kBT∼Δ (Δ is the single-particle mean level spacing).
This sensitivity arises because: 1) exchange reduces the
minimum energy of excitation from the ground state, and 2)
the entropic contribution depends on the change of the spin
of the quantum dot. Including the leading corrections to the
universal Hamiltonian yields results in quantitative
agreement with the experiments. Surprisingly, temperature
appears to be the most important effect.},
Key = {Usaj01}
}
@booklet{Rubio01,
Author = {Rubio, J and Pfeiffer, L and Szymanska, MH and Pinczuk, A and He, S and Baranger, HU and Littlewood, PB and West, KW and Dennis,
BS},
Title = {Coexistence of excitonic lasing with electron-hole plasma
spontaneous emission in one-dimensional semiconductor
structures},
Journal = {Solid State Communications},
Volume = {120},
Number = {11},
Pages = {423-427},
Publisher = {Elsevier BV},
Year = {2001},
Month = {November},
ISSN = {0038-1098},
url = {http://dx.doi.org/10.1016/S0038-1098(01)00418-5},
Abstract = {We report that excitonic lasing gain coexists with
spontaneous optical emission characteristic of an
electron-hole plasma in highly photoexcited one-dimensional
semiconductors. The experiments probe quantum T-wire laser
structures optimized for high photoexcitation. Evidence of
dense electron-hole plasma is clearly seen in the
spontaneous recombination measured when lasing emission
displays distinct excitonic character. These findings differ
strikingly from those in higher dimentional semiconductors,
and offer insights on optical processes considered by recent
theories of dense electron-hole plasmas. © 2001 Published
by Elsevier Science Ltd.},
Doi = {10.1016/S0038-1098(01)00418-5},
Key = {Rubio01}
}
@booklet{Ullmo01,
Author = {Ullmo, D and Baranger, HU},
Title = {Interactions in chaotic nanoparticles: Fluctuations in
Coulomb blockade peak spacings},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {64},
Number = {24},
Pages = {2453241-24532413},
Year = {2001},
Month = {December},
ISSN = {0163-1829},
url = {http://arxiv.org/abs/cond-mat/0103098v1},
Abstract = {We use random matrix models and a Fermi-liquid approach to
investigate the ground state energy of electrons confined to
a nanoparticle. Our expression for the energy includes the
charging effect, the single-particle energies, and the
residual screened interactions treated in Hartree-Fock. This
model is applicable to chaotic quantum dots or nanoparticles
- in these systems the single-particle statistics follows
random matrix theory at energy scales less than the Thouless
energy. We find the distribution of Coulomb blockade peak
spacings first for a large dot in which the residual
interactions can be taken constant: the spacing fluctuations
are of order the mean level separation Δ. Corrections to
this limit are studied using the small parameter 1/kFL: both
the residual interactions and the effect of the changing
confinement on the single-particle levels produce
fluctuations of order Δ/√kFL. The distributions we find
are qualitatively similar to the experimental results. Thus,
models beyond Fermi-liquid theory are not needed to describe
this quantity.},
Doi = {10.1103/PhysRevB.64.245324},
Key = {Ullmo01}
}
@article{fds303608,
Author = {Narimanov, EE and Baranger, HU and Cerruti, NR and Tomsovic,
S},
Title = {Semiclassical theory of Coulomb blockade peak heights in
chaotic quantum dots},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {64},
Number = {23},
Pages = {2353291-23532913},
Publisher = {American Physical Society (APS)},
Year = {2001},
Month = {December},
url = {http://arxiv.org/abs/cond-mat/0101034v1},
Abstract = {We develop a semiclassical theory of Coulomb blockade peak
heights in chaotic quantum dots. Using Berry's conjecture,
we calculate peak height distributions and correlation
functions. We demonstrate that corrections to the
corresponding results of the standard statistical theory are
nonuniversal, and can be expressed in terms of the classical
periodic orbits of the dot that are well coupled to the
leads. The main effect is an oscillatory dependence of the
peak heights on any parameter which is varied; it is
substantial for both symmetric and asymmetric lead
placement. Surprisingly, these dynamical effects do not
influence the full distribution of peak heights, but are
clearly seen in the correlation function or power spectrum.
For nonzero temperature, the correlation function obtained
theoretically is consistent with that measured
experimentally.},
Doi = {10.1103/PhysRevB.64.235329},
Key = {fds303608}
}
@booklet{Usaj02,
Author = {Usaj, G and Baranger, HU},
Title = {Spin and e-e interactions in quantum dots: Leading order
corrections to universality and temperature
effects},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {66},
Number = {15},
Pages = {1553331-15533315},
Year = {2002},
ISSN = {0163-1829},
url = {http://arxiv.org/abs/cond-mat/0203074v1},
Abstract = {We study the statistics of the spacing between Coulomb
blockade conductance peaks in quantum dots with large
dimensionless conductance g. Our starting point is the
"universal Hamiltonian" - valid in the g → ∞ limit -
which includes the charging energy, the single-electron
energies (described by random matrix theory), and the
average exchange interaction. We then calculate the
magnitude of the most relevant finite g corrections, namely,
the effect of surface charge, the "gate" effect, and the
fluctuation of the residual e-e interaction. The resulting
zero-temperature peak spacing distribution has corrections
of order Δ/√g. For typical values of the e-e interaction
(rs∼1) and simple geometries, theory predicts an
asymmetric distribution with a significant even/odd effect.
The width of the distribution is of order 0.3Δ, and its
dominant feature is a large peak for the odd case,
reminiscent of the δ function in the g→∞ limit. We
consider finite temperature effects next. Only after their
inclusion is good agreement with the experimental results
obtained. Even relatively low temperature causes large
modifications in the peak spacing distribution: (i) its peak
is dominated by the even distribution at kBT∼0.3Δ (at
lower T a double peak appears), (ii) the even/odd effect is
considerably weaker, (iii) the δ function is completely
washed out, and (v) fluctuation of the coupling to the leads
becomes relevant. Experiments aimed at observing the T=0
peak spacing distribution should therefore be done at
kBT<0.1Δ for typical values of the e-e
interaction.},
Doi = {10.1103/PhysRevB.66.155333},
Key = {Usaj02}
}
@article{fds341048,
Author = {Usaj, G and Baranger, HU},
Title = {Spin and (formula presented) interactions in quantum dots:
Leading order corrections to universality and temperature
effects},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {66},
Number = {15},
Pages = {1-15},
Year = {2002},
Month = {January},
url = {http://dx.doi.org/10.1103/PhysRevB.66.155333},
Abstract = {We study the statistics of the spacing between Coulomb
blockade conductance peaks in quantum dots with large
dimensionless conductance g. Our starting point is the
“universal Hamiltonian”-valid in the (formula presented)
limit-which includes the charging energy, the
single-electron energies (described by random matrix
theory), and the average exchange interaction. We then
calculate the magnitude of the most relevant finite g
corrections, namely, the effect of surface charge, the
“gate” effect, and the fluctuation of the residual
(formula presented) interaction. The resulting
zero-temperature peak spacing distribution has corrections
of order (formula presented) For typical values of the
(formula presented) interaction (formula presented) and
simple geometries, theory predicts an asymmetric
distribution with a significant even/odd effect. The width
of the distribution is of order (formula presented) and its
dominant feature is a large peak for the odd case,
reminiscent of the (formula presented) function in the
(formula presented) limit. We consider finite temperature
effects next. Only after their inclusion is good agreement
with the experimental results obtained. Even relatively low
temperature causes large modifications in the peak spacing
distribution: (i) its peak is dominated by the even
distribution at (formula presented) (at lower T a double
peak appears), (ii) the even/odd effect is considerably
weaker, (iii) the (formula presented) function is completely
washed out, and (v) fluctuation of the coupling to the leads
becomes relevant. Experiments aimed at observing the
(formula presented) peak spacing distribution should
therefore be done at (formula presented) for typical values
of the (formula presented) interaction. © 2002 The American
Physical Society.},
Doi = {10.1103/PhysRevB.66.155333},
Key = {fds341048}
}
@booklet{Mello02,
Author = {Mello, PA and Baranger, HU},
Title = {Statistical wave scattering: From the atomic nucleus to
mesoscopic systems to microwave cavities},
Journal = {Physica A: Statistical Mechanics and its
Applications},
Volume = {306},
Number = {1-4},
Pages = {323-333},
Publisher = {Elsevier BV},
Year = {2002},
Month = {April},
ISSN = {0378-4371},
url = {http://dx.doi.org/10.1016/S0378-4371(02)00509-5},
Abstract = {Universal statistical aspects of wave scattering by a
variety of physical systems ranging from atomic nuclei to
mesoscopic systems and microwave cavities are described. A
statistical model for the scattering matrix, introduced in
the past in the context of nuclear physics, is employed to
address the problem of quantum chaotic scattering. The main
application of the model is the analysis of electronic
transport through ballistic mesoscopic cavities: it
describes well the results from the numerical solutions of
the Schrödinger equation for two-dimensional systems. ©
2002 Published by Elsevier Science B.V.},
Doi = {10.1016/S0378-4371(02)00509-5},
Key = {Mello02}
}
@booklet{Kaul03,
Author = {Kaul, RK and Ullmo, D and Baranger, HU},
Title = {Mesoscopic fluctuations in quantum dots in the Kondo
regime},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {68},
Number = {16},
Pages = {1613051-1613054},
Year = {2003},
ISSN = {0163-1829},
Abstract = {Properties of the Kondo effect in quantum dots depend
sensitively on the coupling parameters and so on the
realization of the quantum dot-the Kondo temperature itself
becomes a mesoscopic quantity. Assuming chaotic dynamics in
the dot, we use random matrix theory to calculate the
distribution of both the Kondo temperature and the
conductance in the Coulomb blockade regime. We study two
experimentally relevant cases: leads with single channels
and leads with many channels. In the single-channel case,
the distribution of the conductance is very wide as TK
fluctuates on a logarithmic scale. As the number of channels
increases, there is a slow crossover to a self-averaging
regime.},
Key = {Kaul03}
}
@booklet{Jiang03a,
Author = {H. Jiang and H. U. Baranger and W. Yang},
Title = {Spin and conductance-peak-spacing distributions in large
quantum dots: A density-functional theory
study},
Journal = {Physical Review Letters},
Volume = {90},
Number = {2},
Year = {2003},
Month = {January},
Key = {Jiang03a}
}
@article{fds303607,
Author = {Kaul, K and Ullmo, D and Baranger, HU},
Title = {Mesoscopic fluctuations in quantum dots in the Kondo
regime},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {68},
Number = {16},
Pages = {161305},
Publisher = {American Physical Society (APS)},
Year = {2003},
Month = {January},
url = {http://arxiv.org/abs/cond-mat/0306074v2},
Abstract = {Properties of the Kondo effect in quantum dots depend
sensitively on the coupling parameters and so on the
realization of the quantum dot—the Kondo temperature
itself becomes a mesoscopic quantity. Assuming chaotic
dynamics in the dot, we use random matrix theory to
calculate the distribution of both the Kondo temperature and
the conductance in the Coulomb blockade regime. We study two
experimentally relevant cases: leads with single channels
and leads with many channels. In the single-channel case,
the distribution of the conductance is very wide as TK
fluctuates on a logarithmic scale. As the number of channels
increases, there is a slow crossover to a self-averaging
regime. © 2003 The American Physical Society.},
Doi = {10.1103/PhysRevB.68.161305},
Key = {fds303607}
}
@booklet{Usaj03,
Author = {Usaj, G and Baranger, HU},
Title = {Exchange and the Coulomb blockade: Peak height statistics in
quantum dots},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {67},
Number = {12},
Pages = {4},
Publisher = {American Physical Society (APS)},
Year = {2003},
Month = {January},
ISSN = {0163-1829},
url = {http://www.phy.duke.edu/research/cm/bg/paper/usajb03_exch.pdf},
Abstract = {We study the effect of the exchange interaction on the
Coulomb blockade peak height statistics in chaotic quantum
dots. Since exchange reduces the level repulsion in the
many-body spectrum, it strongly affects the fluctuations of
the peak conductance at finite temperature. We find that
including exchange substantially improves the description of
the experimental data. Moreover, it provides further
evidence of the presence of high-spin states (formula
presented) in such systems. © 2003 The American Physical
Society.},
Doi = {10.1103/PhysRevB.67.121308},
Key = {Usaj03}
}
@article{fds245187,
Author = {Jiang, H and Baranger, HU and Yang, W},
Title = {Spin and conductance-peak-spacing distributions in large
quantum dots: a density-functional theory
study.},
Journal = {Physical review letters},
Volume = {90},
Number = {2},
Pages = {026806},
Year = {2003},
Month = {January},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/12570571},
Abstract = {We use spin-density-functional theory to study the spacing
between conductance peaks and the ground-state spin of 2D
model quantum dots with up to 200 electrons. Distributions
for different ranges of electron number are obtained in both
symmetric and asymmetric potentials. The even/odd effect is
pronounced for small symmetric dots but vanishes for large
asymmetric ones, suggesting substantially stronger
interaction effects than expected. The fraction of high-spin
ground states is remarkably large.},
Doi = {10.1103/physrevlett.90.026806},
Key = {fds245187}
}
@booklet{Ke03,
Author = {Ke, S-H and Baranger, HU and Yang, W},
Title = {Addition energies of fullerenes and carbon nanotubes as
quantum dots: the role of symmetry.},
Journal = {Physical review letters},
Volume = {91},
Number = {11},
Pages = {116803},
Year = {2003},
Month = {September},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/14525451},
Abstract = {Using density-functional theory calculations, we investigate
the addition energy (AE) of quantum dots formed of
fullerenes or closed single-wall carbon nanotubes. We focus
on the connection between symmetry and oscillations in the
AE spectrum. In the highly symmetric fullerenes the
oscillation period is large because of the large level
degeneracy and Hund's rule. For long nanotubes, the AE
oscillation is fourfold. Adding defects destroys the spatial
symmetry of the tubes, leaving only spin degeneracy;
correspondingly, the fourfold behavior is destroyed, leaving
an even/odd behavior which is quite robust. We use our
symmetry results to explain recent experiments.},
Doi = {10.1103/physrevlett.91.116803},
Key = {Ke03}
}
@article{fds245188,
Author = {Jiang, H and Baranger, HU and Yang, W},
Title = {Density Functional Theory Simulation of Large Quantum
Dots},
Journal = {Phys. Rev. B},
Volume = {68},
Number = {16},
Pages = {165337-165337},
Publisher = {American Physical Society},
Year = {2003},
Month = {October},
ISSN = {1098-0121},
url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000186571800068&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
Abstract = {Kohn-Sham spin-density functional theory provides an
efficient and accurate model to study electron-electron
interaction effects in quantum dots, but its application to
large systems is a challenge. Here an efficient method for
the simulation of quantum dots using density-function theory
is developed; it includes the particle-in-the-box
representation of the Kohn-Sham orbitals, an efficient
conjugate-gradient method to directly minimize the total
energy, a Fourier convolution approach for the calculation
of the Hartree potential, and a simplified multigrid
technique to accelerate the convergence. We test the
methodology in a two-dimensional model system and show that
numerical studies of large quantum dots with several hundred
electrons become computationally affordable. In the
noninteracting limit, the classical dynamics of the system
we study can be continuously varied from integrable to fully
chaotic. The qualitative difference in the noninteracting
classical dynamics has an effect on the quantum properties
of the interacting system: integrable classical dynamics
leads to higher-spin states and a broader distribution of
spacing between Coulomb blockade peaks.},
Doi = {10.1103/PhysRevB.68.165337},
Key = {fds245188}
}
@article{Vorojtsov04_multielecqubits,
Author = {Vorojtsov, S and Mucciolo, ER and Baranger, HU},
Title = {Spin qubits in multielectron quantum dots},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {69},
Number = {11},
Pages = {1153291-1153296},
Year = {2004},
ISSN = {0163-1829},
url = {http://arxiv.org/abs/cond-mat/0308118v3},
Keywords = {quantum dots; mesoscopic systems; exchange interactions
(electron); electron spin; quantum computing},
Abstract = {We study the effect of mesoscopic fluctuations on the
magnitude of errors that can occur in exchange operations on
quantum dot spin qubits. Midsize double quantum dots, with
an odd number of electrons in the range of a few tens in
each dot, are investigated through the constant interaction
model using realistic parameters. It is found that the
constraint of having short pulses and small errors implies
keeping accurate control, at the few percent level, of
several electrode voltages. In practice, the number of
independent parameters per dot that one should tune depends
on the configuration and ranges from one to
four.},
Doi = {10.1103/PhysRevB.69.115329},
Key = {Vorojtsov04_multielecqubits}
}
@article{Ke04_molectrans1,
Author = {Ke, SH and Baranger, HU and Yang, W},
Title = {Electron Transport Through Molecules: Self-Consistent and
Non-Self-Consistent Approaches},
Journal = {Phys. Rev. B},
Volume = {70},
Number = {8},
Pages = {085410},
Publisher = {American Physical Society (APS)},
Year = {2004},
url = {http://www.phy.duke.edu/research/cm/bg/paper/jianguyb04_dftreal1.pdf},
Keywords = {density functional theory; Green's function methods;
transport processes; molecular electronics; carbon;
aluminium; contact potential},
Abstract = {A self-consistent method for calculating electron transport
through a molecular device is developed. It is based on
density functional theory electronic structure calculations
under periodic boundary conditions and implemented in the
framework of the nonequilibrium Green function approach. To
avoid the substantial computational cost in finding the I-V
characteristic of large systems, we also develop an
approximate but much more efficient non-self-consistent
method. Here the change in effective potential in the device
region caused by a bias is approximated by the main features
of the voltage drop. As applications, the I-V curves of a
carbon chain and an aluminum chain sandwiched between two
aluminum electrodes are calculated-two systems in which the
voltage drops very differently. By comparing to the
self-consistent results, we show that this
non-self-consistent approach works well and can give
quantitatively good results.},
Doi = {10.1103/PhysRevB.70.085410},
Key = {Ke04_molectrans1}
}
@article{Ullmo04_sdftstrutinsky,
Author = {Ullmo, D and Jiang, H and Yang, W and Baranger, HU},
Title = {Landau Fermi Liquid Picture of Spin Density Functional
Theory: Strutinsky Approach to Quantum Dots},
Journal = {Phys. Rev. B},
Volume = {70},
Number = {20},
Pages = {205309},
Publisher = {American Physical Society (APS)},
Year = {2004},
ISSN = {0163-1829},
url = {http://www.phy.duke.edu/research/cm/bg/paper/ullmojyb04_dftstr.pdf},
Abstract = {We analyze the ground-state energy and spin of quantum dots
obtained from spin density functional theory (SDFT)
calculations. First, we introduce a Strutinsky-type
approximation, in which quantum interference is treated as a
correction to a smooth Thomas-Fermi description. For large
irregular dots, we find that the second-order Strutinsky
expressions have an accuracy of about 5% of a mean level
spacing compared to the full SDFT and capture all the
qualitative features. Second, we perform a random
matrix-theory/random-plane wave analysis of the Strutinsky
SDFT expressions. The results are statistically similar to
the SDFT quantum dot statistics. Finally, we note that the
second-order Strutinsky approximation provides, in essence,
a Landau Fermi-liquid picture of spin density functional
theory. For instance, the leading term in the spin channel
is simply the familiar exchange constant. A direct
comparison between SDFT and the perturbation theory derived
"universal Hamiltonian" is thus made possible.},
Doi = {10.1103/PhysRevB.70.205309},
Key = {Ullmo04_sdftstrutinsky}
}
@article{Jiang04_statistics,
Author = {Jiang, H and Ullmo, D and Yang, W and Baranger, HU},
Title = {Electron-Electron Interactions in Isolated and Realistic
Quantum Dots: A Density Functional Theory
Study},
Journal = {Phys. Rev. B},
Volume = {69},
Number = {23},
Pages = {235326},
Publisher = {American Physical Society (APS)},
Year = {2004},
ISSN = {0163-1829},
url = {http://www.phy.duke.edu/research/cm/bg/paper/jianguyb04_dftreal1.pdf},
Keywords = {quantum dots; electron-electron interactions; density
functional theory; spin dynamics},
Abstract = {We use Kohn-Sham spin-density-functional theory to study the
statistics of ground-state spin and the spacing between
conductance peaks in the Coulomb blockade regime for both
two-dimensional isolated and realistic quantum dots. We make
a systematic investigation of the effects of
electron-electron interaction strength and electron number
on both the peak spacing and spin distributions. A direct
comparison between the distributions from isolated and
realistic dots shows that, despite the difference in the
boundary conditions and confining potential, the statistical
properties are qualitatively the same. Strong even/odd
pairing in the peak spacing distribution is observed only in
the weak e-e interaction regime and vanishes for moderate
interactions. The probability of high spin ground states
increases for stronger e-e interaction and seems to saturate
around rs ∼4. The saturated value is larger than previous
theoretical predictions. Both spin and conductance peak
spacing distributions show substantial variation as the
electron number increases, not saturating until N ∼150. To
interpret our numerical results, we analyze the spin
distribution in the even N case using a simple two-level
model.},
Doi = {10.1103/PhysRevB.69.235326},
Key = {Jiang04_statistics}
}
@article{fds318400,
Author = {Kaul, RK and Ullmo, D and Baranger, HU},
Title = {Publisher’s Note: Mesoscopic fluctuations in quantum dots
in the Kondo regime [Phys. Rev. B 68, 161305
(2003)]},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {69},
Number = {8},
Publisher = {American Physical Society (APS)},
Year = {2004},
Month = {January},
url = {http://dx.doi.org/10.1103/PhysRevB.69.089902},
Doi = {10.1103/PhysRevB.69.089902},
Key = {fds318400}
}
@article{fds245061,
Author = {Kaul, RK and Ullmo, D and Baranger, HU},
Title = {Erratum: Mesoscopic fluctuations in quantum dots in the
Kondo regime (Physical Review B - Condensed Matter and
Materials Physics (October 14, 2003) 68 (161305) (DOI:
10.1103/PhysRevB.69.089902))},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {69},
Number = {8},
Pages = {899021},
Year = {2004},
Month = {February},
ISSN = {0163-1829},
Key = {fds245061}
}
@article{fds245167,
Author = {Hentschel, M and Ullmo, D and Baranger, HU},
Title = {Fermi-edge singularities in the mesoscopic x-ray edge
problem.},
Journal = {Physical review letters},
Volume = {93},
Number = {17},
Pages = {176807},
Publisher = {cond-mat/0402207},
Year = {2004},
Month = {October},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/15525108},
Abstract = {We study the x-ray edge problem for a chaotic quantum dot or
nanoparticle displaying mesoscopic fluctuations. In the
bulk, x-ray physics is known to produce Fermi-edge
singularities-deviations from the naively expected
photoabsorption cross section in the form of a peaked or
rounded edge. For a coherent system with chaotic dynamics,
we find substantial changes; in particular, a
photoabsorption cross section showing a rounded edge in the
bulk will change to a slightly peaked edge on average as the
system size is reduced to a mesoscopic (coherent)
scale.},
Doi = {10.1103/physrevlett.93.176807},
Key = {fds245167}
}
@article{Ke04_molectrans2,
Author = {Ke, S-H and Baranger, HU and Yang, W},
Title = {Molecular conductance: chemical trends of anchoring
groups.},
Journal = {Journal of the American Chemical Society},
Volume = {126},
Number = {48},
Pages = {15897-15904},
Year = {2004},
Month = {December},
ISSN = {0002-7863},
url = {http://www.ncbi.nlm.nih.gov/pubmed/15571415},
Abstract = {Combining density functional theory calculations for
molecular electronic structure with a Green function method
for electron transport, we calculate from first principles
the molecular conductance of benzene connected to two Au
leads through different anchoring atoms-S, Se, and Te. The
relaxed atomic structure of the contact, different lead
orientations, and different adsorption sites are fully
considered. We find that the molecule-lead coupling,
electron transfer, and conductance all depend strongly on
the adsorption site, lead orientation, and local contact
atomic configuration. For flat contacts the conductance
decreases as the atomic number of the anchoring atom
increases, regardless of the adsorption site, lead
orientation, or bias. For small bias this chemical trend is,
however, dependent on the contact atomic configuration: an
additional Au atom at the contact with the (111) lead
changes the best anchoring atom from S to Se, although for
large bias the original chemical trend is
recovered.},
Doi = {10.1021/ja047367e},
Key = {Ke04_molectrans2}
}
@article{Jiang04_scrambling,
Author = {Jiang, H and Ullmo, D and Yang, W and Baranger, HU},
Title = {Scrambling and Gate Effects in Realistic Quantum
Dots},
Journal = {Phys. Rev. B},
Volume = {71},
Number = {8},
Pages = {085313},
Publisher = {(cond-mat/0405262)},
Year = {2005},
url = {http://arxiv.org/abs/cond-mat/0405262v2},
Abstract = {We evaluate the magnitude of two important mesoscopic
effects using a realistic model of typical quantum dots.
"Scrambling" and "gate effect" are defined as the change in
the single-particle spectrum due to added electrons or
gate-induced shape deformation, respectively. These two
effects are investigated systematically in both the
'self-consistent Kohn-Sham (KS) theory and a Fermi
liquidlike Strutinsky approach. We find that the genuine
scrambling effect is small because the potential here is
smooth. In the KS theory, a key point is the implicit
inclusion of residual interactions in the spectrum; these
dominate and make scrambling appear larger. Finally, the
gate effect is comparable in the two cases and, while small,
is able to cause gate-induced spin transitions. ©2005 The
American Physical Society.},
Doi = {10.1103/PhysRevB.71.085313},
Key = {Jiang04_scrambling}
}
@article{fds245108,
Author = {Ullmo, D and Jiang, H and Yang, W and Baranger, HU},
Title = {Interactions and Broken Time-Reversal Symmetry in Chaotic
Quantum Dots},
Journal = {Phys. Rev. B},
Volume = {71},
Number = {20},
Pages = {201310(R)},
Publisher = {American Physical Society (APS)},
Year = {2005},
url = {http://www.phy.duke.edu/research/cm/bg/paper/ullmojyb04_finiteb.pdf},
Abstract = {When treating interactions in quantum dots within a
random-phase- approximation (RPA)-like approach,
time-reversal symmetry plays an important role as
higher-order terms-the Cooper series-need to be included
when this symmetry is present. Here we consider model
quantum dots in a magnetic field weak enough to leave the
dynamics of the dot chaotic, but strong enough to break
time-reversal symmetry. The ground-state spin and addition
energy for dots containing 120-200 electrons are found using
local spin-density-functional theory, and we compare the
corresponding distributions with those derived from an
RPA-like treatment of the interactions. The agreement
between the two approaches is very good, significantly
better than for analogous calculations in the presence of
time-reversal-symmetry. This demonstrates that the
discrepancies between the two approaches in the
time-reversal symmetric case indeed originate from the
Cooper channel, indicating that these higher-order terms
might not be properly taken into account in the
spin-density-functional calculations. © 2005 The American
Physical Society.},
Doi = {10.1103/PhysRevB.71.201310},
Key = {fds245108}
}
@article{fds245112,
Author = {Yoo, J and Chandrasekharan, S and Kaul, RK and Ullmo, D and Baranger,
HU},
Title = {On the Sign Problem in the Hirsch-Fye Algorithm for Impurity
Problems},
Journal = {J. Phys. A: Math. and General},
Volume = {38},
Number = {48},
Pages = {10307},
Publisher = {cond-mat/0412771},
Year = {2005},
url = {http://www.phy.duke.edu/research/cm/bg/paper/YooCKUB05_noHFsign.pdf},
Abstract = {We show that there is no fermion sign problem in the Hirsch
and Fye algorithm for the single-impurity Anderson model.
Beyond the particle-hole symmetric case for which a simple
proof exists, this has been known only empirically. Here we
prove the nonexistence of a sign problem for the general
case by showing that each spin trace for a given Ising
configuration is separately positive. We further use this
insight to analyse under what conditions orbitally
degenerate Anderson models or the two-impurity Anderson
model develop a sign. © 2005 IOP Publishing
Ltd.},
Doi = {10.1088/0305-4470/38/48/004},
Key = {fds245112}
}
@article{fds245115,
Author = {Kaul, RK and Ullmo, D and Chandrasekharan, S and Baranger,
HU},
Title = {Mesoscopic Kondo Problem},
Journal = {Europhys. Lett.},
Volume = {71},
Number = {6},
Pages = {973},
Publisher = {cond-mat/0409211},
Year = {2005},
url = {http://www.phy.duke.edu/research/cm/bg/paper/kaulucb04_mesokondo.pdf},
Abstract = {We study the effect of mesoscopic fluctuations on a magnetic
impurity coupled to a spatially confined electron gas with a
temperature in the mesoscopic range (i.e. between the mean
level spacing Δ and the Thouless energy ETh). Comparing
"poor-man's scaling" with exact Quantum Monte Carlo, we find
that for temperatures larger than the Kondo temperature,
many aspects of the fluctuations can be captured by the
perturbative technique. Using this technique in conjunction
with semi-classical approximations, we are able to calculate
the mesoscopic fluctuations for a wide variety of systems.
For temperatures smaller than the Kondo temperature, we find
large fluctuations and deviations from the universal
behavior. © EDP Sciences.},
Doi = {10.1209/epl/i2005-10184-1},
Key = {fds245115}
}
@article{fds245116,
Author = {Lee, JW and Chandrasekharan, S and Baranger, HU},
Title = {Quantum Monte Carlo Study of Disordered Fermions},
Journal = {Phys. Rev. B},
Volume = {72},
Number = {2},
Pages = {024525},
Publisher = {cond-mat/0411306},
Year = {2005},
ISSN = {1098-0121},
url = {http://www.phy.duke.edu/research/cm/bg/paper/leecb04_disordfermion.pdf},
Abstract = {We study a strongly correlated fermionic model with
attractive interactions in the presence of disorder in two
spatial dimensions. Our model has been designed so that it
can be solved using the recently discovered meron-cluster
approach. Although the model is unconventional it has the
same symmetries as the Hubbard model. Since the naive
algorithm is inefficient, we develop an algorithm by
combining the meron-cluster technique with the directed-loop
update. This combination allows us to compute the pair
susceptibility and the winding number susceptibility
accurately. We find that the s -wave superconductivity,
present in the clean model, does not disappear until the
disorder reaches a temperature dependent critical strength.
The critical behavior as a function of disorder close to the
phase transition belongs to the Berezinky-Kosterlitz-Thouless
universality class as expected. The fermionic degrees of
freedom, although present, do not appear to play an
important role near the phase transition. © 2005 The
American Physical Society.},
Doi = {10.1103/PhysRevB.72.024525},
Key = {fds245116}
}
@article{fds245118,
Author = {Ghosal, A and Umrigar, CJ and Jiang, H and Ullmo, D and Baranger,
HU},
Title = {Interaction Effects in Irregular Quantum Dots: A Quantum
Monte Carlo Study},
Journal = {Phys. Rev. B},
Volume = {71},
Pages = {241306(R)},
Publisher = {cond-mat/0411242},
Year = {2005},
url = {http://www.phy.duke.edu/research/cm/bg/paper/ghosalujub04_qmcqdot.pdf},
Key = {fds245118}
}
@article{Yoo04_spinchain,
Author = {Yoo, J and Chandrasekharan, S and Kaul, RK and Ullmo, D and Baranger,
HU},
Title = {Cluster Algorithms for Quantum Impurity Models and
Mesoscopic Kondo Physics},
Journal = {Phys. Rev. B},
Volume = {71},
Number = {20},
Pages = {201309(R)},
Publisher = {cond-mat/0411313},
Year = {2005},
url = {http://www.phy.duke.edu/research/cm/bg/paper/yoockub04_clusterqimp.pdf},
Abstract = {Nanoscale physics and dynamical mean-field theory have both
generated increased interest in complex quantum impurity
problems and so have focused attention on the need for
flexible quantum impurity solvers. Here we demonstrate that
the mapping of single-quantum impurity problems onto spin
chains can be exploited to yield a powerful and extremely
flexible impurity solver. We implement this cluster
algorithm explicitly for the Anderson and Kondo
Hamiltonians, and illustrate its use in the "mesoscopic
Kondo problem." To study universal Kondo physics, a large
ratio between the effective bandwidth Deff and the
temperature T is required; our cluster algorithm treats the
mesoscopic fluctuations exactly while being able to approach
the large Deff T limit with ease. We emphasize that the
flexibility of our method allows it to tackle a wide variety
of quantum impurity problems; thus, it may also be relevant
to the dynamical mean-field theory of lattice problems. ©
2005 The American Physical Society.},
Doi = {10.1103/PhysRevB.71.201309},
Key = {Yoo04_spinchain}
}
@article{Yoo04_multilev,
Author = {Yoo, J and Chandrasekharan, S and Baranger, HU},
Title = {A Multi-level Algorithm for Quantum-impurity
Models},
Journal = {Phys. Rev. E},
Volume = {71},
Number = {3 Pt 2B},
Pages = {036708},
Publisher = {cond-mat/0408123},
Year = {2005},
ISSN = {1539-3755},
url = {http://www.ncbi.nlm.nih.gov/pubmed/15903634},
Abstract = {A continuous-time path integral quantum Monte Carlo method
using the directed-loop algorithm is developed to simulate
the Anderson single-impurity model in the occupation number
basis. Although the method suffers from a sign problem at
low temperatures, the new algorithm has many advantages over
conventional algorithms. For example, the model can be
easily simulated in the Kondo limit without time
discretization errors. Furthermore, many observables
including the impurity susceptibility and a variety of
fermionic observables can be calculated efficiently. Finally
the new approach allows us to explore a general technique,
called the multilevel algorithm, to solve the sign problem.
We find that the multilevel algorithm is able to generate an
exponentially large number of configurations with an effort
that grows as a polynomial in inverse temperature such that
configurations with a positive sign dominate over those with
negative signs. Our algorithm can be easily generalized to
other multi-impurity problems.},
Doi = {10.1103/physreve.71.036708},
Key = {Yoo04_multilev}
}
@article{Ke04_molecgate,
Author = {Ke, SH and Baranger, HU and Yang, W},
Title = {Electron Transport Through Molecules: Gate Induced
Polarization and Potential Shift},
Journal = {Phys. Rev. B},
Volume = {71},
Number = {11},
Pages = {113401},
Publisher = {cond-mat/046640},
Year = {2005},
ISSN = {1098-0121},
url = {http://www.phy.duke.edu/research/cm/bg/paper/keby04_gatepolar.pdf},
Abstract = {We analyze the effect of a gate on the conductance of
molecules by separately evaluating the gate-induced
polarization and the potential shift of the molecule
relative to the leads. The calculations use ab initio
density functional theory combined with a Green function
method for electron transport. For a general view, we study
several systems: (1) atomic chains of C or Al sandwiched
between Al electrodes, (2) a benzene molecule between Au
leads, and (3) (9,0) and (5,5) carbon nanotubes. We find
that the polarization effect is small because of screening,
while the effect of the potential shift is significant,
providing a mechanism for single-molecule transistors.
©2005 The American Physical Society.},
Doi = {10.1103/PhysRevB.71.113401},
Key = {Ke04_molecgate}
}
@article{fds245064,
Author = {Usaj, G and Baranger, HU},
Title = {Erratum: Mesoscopic tunneling magnetoresistance (Physical
Review B- Condensed Matter and Materials Physics (2001) 63
(184418))},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {71},
Number = {17},
Publisher = {American Physical Society (APS)},
Year = {2005},
Month = {January},
url = {http://dx.doi.org/10.1103/PhysRevB.71.179903},
Doi = {10.1103/PhysRevB.71.179903},
Key = {fds245064}
}
@article{fds245120,
Author = {Vorojtsov, S and Mucciolo, ER and Baranger, HU},
Title = {Phonon decoherence of a double quantum dot charge
qubit},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {71},
Number = {20},
Pages = {205322},
Publisher = {American Physical Society (APS)},
Year = {2005},
Month = {January},
url = {http://www.phy.duke.edu/research/cm/bg/paper/vorojtsovmb04_ddot.pdf},
Abstract = {We study decoherence of a quantum dot charge qubit due to
coupling to piezoelectric acoustic phonons in the
Born-Markov approximation. After including appropriate form
factors, we find that phonon decoherence rates are one to
two orders of magnitude weaker than was previously
predicted. We calculate the dependence of the Q factor on
lattice temperature, quantum dot size, and interdot
coupling. Our results suggest that mechanisms other than
phonon decoherence play a more significant role in current
experimental setups. © 2005 The American Physical
Society.},
Doi = {10.1103/PhysRevB.71.205322},
Key = {fds245120}
}
@article{Liu04_molecinter,
Author = {Liu, R and Ke, S-H and Baranger, HU and Yang, W},
Title = {Intermolecular effect in molecular electronics.},
Journal = {The Journal of chemical physics},
Volume = {122},
Number = {4},
Pages = {44703},
Year = {2005},
Month = {January},
ISSN = {0021-9606},
url = {http://www.ncbi.nlm.nih.gov/pubmed/15740279},
Abstract = {We investigate the effects of lateral interactions on the
conductance of two molecules connected in parallel to
semi-infinite leads. The method we use combines a Green
function approach to quantum transport with density
functional theory for the electronic properties. The system,
modeled after a self-assembled monolayer, consists of
benzylmercaptane molecules sandwiched between gold
electrodes. We find that the conductance increases when
intermolecular interaction comes into play. The source of
this increase is the indirect interaction through the gold
substrate rather than direct molecule-molecule interaction.
A striking resonance is produced only 0.3 eV above the Fermi
energy.},
Doi = {10.1063/1.1825377},
Key = {Liu04_molecinter}
}
@article{Ke04_molectrans3,
Author = {Ke, S-H and Baranger, HU and Yang, W},
Title = {Contact atomic structure and electron transport through
molecules.},
Journal = {The Journal of chemical physics},
Volume = {122},
Number = {7},
Pages = {074704},
Publisher = {cond-mat/0405047},
Year = {2005},
Month = {February},
ISSN = {0021-9606},
url = {http://www.ncbi.nlm.nih.gov/pubmed/15743262},
Abstract = {Using benzene sandwiched between two Au leads as a model
system, we investigate from first principles the change in
molecular conductance caused by different atomic structures
around the metal-molecule contact. Our motivation is the
variable situations that may arise in break junction
experiments; our approach is a combined density functional
theory and Green function technique. We focus on effects
caused by (1) the presence of an additional Au atom at the
contact and (2) possible changes in the molecule-lead
separation. The effects of contact atomic relaxation and two
different lead orientations are fully considered. We find
that the presence of an additional Au atom at each of the
two contacts will increase the equilibrium conductance by up
to two orders of magnitude regardless of either the lead
orientation or different group-VI anchoring atoms. This is
due to a resonance peak near the Fermi energy from the
lowest energy unoccupied molecular orbital. In the
nonequilibrium properties, the resonance peak manifests
itself in a negative differential conductance. We find that
the dependence of the equilibrium conductance on the
molecule-lead separation can be quite subtle: either very
weak or very strong depending on the separation
regime.},
Doi = {10.1063/1.1851496},
Key = {Ke04_molectrans3}
}
@article{fds245066,
Author = {Ghosal, A and Umrigar, CJ and Jiang, H and Ullmo, D and Baranger,
HU},
Title = {Interaction effects in the mesoscopic regime: A quantum
Monte Carlo study of irregular quantum dots},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {71},
Number = {24},
Publisher = {American Physical Society (APS)},
Year = {2005},
Month = {June},
ISSN = {1098-0121},
url = {http://dx.doi.org/10.1103/PhysRevB.71.241306},
Abstract = {We address the issue of accurately treating interaction
effects in the mesoscopic regime by investigating the
ground-state properties of isolated irregular quantum dots.
Quantum Monte Carlo techniques are used to calculate the
distributions of ground-state spin and addition energy. We
find a reduced probability of high spin and a somewhat
larger even/odd alternation in the addition energy from
quantum Monte Carlo than in local spin-density-functional
theory. In both approaches, the even/odd effect gets smaller
with increasing number of electrons, contrary to the
theoretical understanding of large dots. We argue that the
local spin-density approximation overpredicts the effects of
interactions in quantum dots. © 2005 The American Physical
Society.},
Doi = {10.1103/PhysRevB.71.241306},
Key = {fds245066}
}
@article{fds245119,
Author = {Getty, SA and Engtrakul, C and Wang, L and Liu, R and Ke, SH and Baranger,
HU and Yang, W and Fuhrer, MS and Sita, LR},
Title = {Near-perfect conduction through a ferrocene-based molecular
wire},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {71},
Number = {24},
Pages = {241401(R)},
Publisher = {American Physical Society (APS)},
Year = {2005},
Month = {June},
ISSN = {1098-0121},
url = {http://www.phy.duke.edu/research/cm/bg/paper/GettyEWLKBYMS05_ferrocene.pdf},
Abstract = {Here we describe the design, single-molecule transport
measurements, and theoretical modeling of a ferrocene-based
organometallic molecular wire, whose bias-dependent
conductance shows a clear Lorentzian form with magnitude
exceeding 70% of the conductance quantum G0. We attribute
this unprecedented level of single-molecule conductance to a
manifestation of the low-lying molecular resonance and
extended orbital network long predicted for a conjugated
organic system. A similar-in-length, all-organic conjugated
phenylethynyl oligomer molecular framework shows much lower
conductance. © 2005 The American Physical
Society.},
Doi = {10.1103/PhysRevB.71.241401},
Key = {fds245119}
}
@article{fds245117,
Author = {Miller, M and Ullmo, D and Baranger, HU},
Title = {Statistics of wave functions in disordered systems with
applications to Coulomb blockade peak spacing},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {72},
Number = {4},
Pages = {045305},
Publisher = {American Physical Society (APS)},
Year = {2005},
Month = {July},
ISSN = {1098-0121},
url = {http://www.phy.duke.edu/research/cm/bg/paper/millerub04_psistats.pdf},
Abstract = {Despite considerable work on the energy-level and wave
function statistics of disordered quantum systems, numerical
studies of those statistics relevant for electron-electron
interactions in mesoscopic systems have been lacking. We
plug this gap by using a tight-binding model to study a wide
variety of statistics for the two-dimensional, disordered
quantum system in the diffusive regime. Our results are in
good agreement with random matrix theory (or its extensions)
for simple statistics such as the probability distribution
of energy levels or spatial correlation of a wave function.
However, we see substantial disagreement in several
statistics which involve both integrating over space and
different energy levels, indicating that disordered systems
are more complex than previously thought. These are exactly
the quantities relevant to electron-electron interaction
effects in quantum dots; in fact, we apply these results to
the Coulomb blockade, where we find altered spacings between
conductance peaks and wider spin distributions than
traditionally expected. © 2005 The American Physical
Society.},
Doi = {10.1103/PhysRevB.72.045305},
Key = {fds245117}
}
@article{fds245122,
Author = {Hentschel, M and Ullmo, D and Baranger, HU},
Title = {Fermi edge singularities in the mesoscopic regime: Anderson
orthogonality catastrophe},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {72},
Number = {3},
Pages = {035310},
Publisher = {American Physical Society (APS)},
Year = {2005},
Month = {July},
ISSN = {1098-0121},
url = {http://www.phy.duke.edu/research/cm/bg/paper/HentschelUB05_aoc.pdf},
Abstract = {For generic mesoscopic systems, such as quantum dots or
nanoparticles, we study the Anderson orthogonality
catastrophe (AOC) and Fermi-edge singularities in
photoabsorption spectra in a series of two papers. In the
present paper we focus on AOC for a finite number of
particles in discrete energy levels where, in contrast to
the bulk situation, AOC is not complete. Moreover,
fluctuations characteristic for mesoscopic systems lead to a
broad distribution of AOC ground-state overlaps. The
fluctuations originate dominantly in the levels around the
Fermi energy, and we derive an analytic expression for the
probability distribution of AOC overlaps in the limit of
strong perturbations. We address the formation of a bound
state and its importance for symmetries between the overlap
distributions for attractive and repulsive potentials. Our
results are based on a random matrix model for the chaotic
conduction electrons that are subject to a rank-one
perturbation corresponding, for example, to the localized
core hole generated in the photoabsorption process. © 2005
The American Physical Society.},
Doi = {10.1103/PhysRevB.72.035310},
Key = {fds245122}
}
@article{fds245113,
Author = {Ke, S-H and Baranger, HU and Yang, W},
Title = {Models of electrodes and contacts in molecular
electronics.},
Journal = {The Journal of chemical physics},
Volume = {123},
Number = {11},
Pages = {114701},
Publisher = {cond-mat/0504089},
Year = {2005},
Month = {September},
ISSN = {0021-9606},
url = {http://www.ncbi.nlm.nih.gov/pubmed/16392577},
Abstract = {Bridging the difference in atomic structure between
experiments and theoretical calculations and exploring
quantum confinement effects in thin electrodes (leads) are
both important issues in molecular electronics. To address
these issues, we report here, by using Au-benzenedithiol-Au
as a model system, systematic investigations of different
models for the leads and the lead-molecule contacts: leads
with different cross sections, leads consisting of infinite
surfaces, and surface leads with a local nanowire or atomic
chain of different lengths. The method adopted is a
nonequilibrium Green's-function approach combined with
density-functional theory calculations for the electronic
structure and transport, in which the leads and molecule are
treated on the same footing. It is shown that leads with a
small cross section will lead to large oscillations in the
transmission function T(E), which depend significantly on
the lead structure (orientation) because of quantum
waveguide effects. This oscillation slowly decays as the
lead width increases, with the average approaching the limit
given by infinite surface leads. Local nanowire structures
around the contacts induce moderate fluctuations in T(E),
while a Au atomic chain (including a single Au apex atom) at
each contact leads to a significant conductance
resonance.},
Doi = {10.1063/1.1993558},
Key = {fds245113}
}
@article{fds245114,
Author = {Usaj, G and Baranger, HU},
Title = {Anisotropy in ferromagnetic nanoparticles: Level-to-level
fluctuations of a collective effect},
Journal = {Europhysics Letters},
Volume = {72},
Number = {1},
Pages = {110-116},
Publisher = {IOP Publishing},
Year = {2005},
Month = {October},
url = {http://www.phy.duke.edu/research/cm/bg/paper/usajb04_ferronanopart.pdf},
Abstract = {We calculate the mesoscopic fluctuations of the magnetic
anisotropy of ferromagnetic nanoparticles; that is, the
effect of single-particle interference on the direction of
the collective magnetic moment. A microscopic spin-orbit
Hamiltonian considered as a perturbation of the much
stronger exchange interaction first yields an explicit
expression for the anisotropy tensor. Then, assuming a
simple random matrix model for the spin-orbit coupling
allows us to describe the fluctuation of such a tensor
analytically. In the case of uniaxial anisotropy, we
calculate the distribution of the anisotropy constant for a
given number of electrons, and its variation upon increasing
this number by one. The magnitude of the latter scales
inversely with the number of atoms in the particle and is
sufficient to account for the experimental data. © EDP
Sciences.},
Doi = {10.1209/epl/i2005-10210-4},
Key = {fds245114}
}
@article{fds245121,
Author = {Liu, R and Ke, S-H and Baranger, HU and Yang, W},
Title = {Organometallic spintronics: dicobaltocene
switch.},
Journal = {Nano letters},
Volume = {5},
Number = {10},
Pages = {1959-1962},
Year = {2005},
Month = {October},
ISSN = {1530-6984},
url = {http://www.ncbi.nlm.nih.gov/pubmed/16218717},
Abstract = {A single-molecule spintronic switch and spin valve using two
cobaltocene moieties is proposed. Spin-dependent transport
through a lead-molecule-lead junction has been calculated
using first-principles density functional and nonequilibrium
Green function methods. We find that the antiparallel
(singlet) configuration of the cobaltocene spins blocks
electron transport near the Fermi energy, while the spin
parallel (triplet) configuration enables much higher
current. The energy difierence between the antiparallel and
parallel states depends on the insulating spacer separating
the two cobaltocenes, allowing switching through the
application of a moderate magnetic field.},
Doi = {10.1021/nl0513380},
Key = {fds245121}
}
@article{fds245111,
Author = {Vorojtsov, S and Baranger, HU},
Title = {Coulomb blockade peak spacings: Interplay of spin and
dot-lead coupling},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {72},
Number = {16},
Pages = {024525},
Publisher = {American Physical Society (APS)},
Year = {2005},
Month = {October},
ISSN = {1098-0121},
url = {http://www.phy.duke.edu/research/cm/bg/paper/VorojtsovB05_dotleadcoup.pdf},
Abstract = {For Coulomb blockade peaks in the linear conductance of a
quantum dot, we study the correction to the spacing between
the peaks due to dot-lead coupling. This coupling can affect
measurements in which Coulomb blockade phenomena are used as
a tool to probe the energy level structure of quantum dots.
The electron-electron interactions in the quantum dot are
described by the constant exchange and interaction (CEI)
model while the single-particle properties are described by
random matrix theory. We find analytic expressions for both
the average and rms mesoscopic fluctuation of the
correction. For a realistic value of the exchange
interaction constant Js, the ensemble average correction to
the peak spacing is two to three times smaller than that at
Js=0. As a function of Js, the average correction to the
peak spacing for an even valley decreases monotonically,
nonetheless staying positive. The rms fluctuation is of the
same order as the average and weakly depends on Js. For a
small fraction of quantum dots in the ensemble, therefore,
the correction to the peak spacing for the even valley is
negative. The correction to the spacing in the odd valleys
is opposite in sign to that in the even valleys and equal in
magnitude. These results are robust with respect to the
choice of the random matrix ensemble or change in parameters
such as charging energy, mean level spacing, or temperature.
© 2005 The American Physical Society.},
Doi = {10.1103/PhysRevB.72.165349},
Key = {fds245111}
}
@article{fds245063,
Author = {Mucciolo, ER and Vorojtsov, S and Baranger, HU},
Title = {Phonon decoherence in quantum dot qubits},
Journal = {Proceedings of SPIE - The International Society for Optical
Engineering},
Volume = {5815},
Pages = {53-61},
Publisher = {SPIE},
Year = {2005},
Month = {November},
ISSN = {0277-786X},
url = {http://dx.doi.org/10.1117/12.603649},
Abstract = {The spin of an electron confined into a lateral
semiconductor quantum dot has been proposed as a possible
physical realization of a qubit. While the spin has the
advantage of large decoherence times, operations with more
than one qubit will necessarily involve orbital degrees of
freedom, namely, charge, which is much more prone to
decoherence. There are also alternative quantum dot qubit
proposals that are entirely based on charge. We have used a
realistic model to quantify the limitations imposed by
acoustic phonons on the operation of quantum dot-based
qubits. Our treatment includes essential aspects of the
setup geometry, wave function profile and materials
characteristics. The time dependence of the qubit density
matrix is the presence of a phonon bath solved within the
Born-Markov approximation. We find that the inclusion of
geometric form factors makes the phonon-induced decoherence
rates in double dot charge qubits nearly one order of
magnitude lower than estimates previously in the literature.
Moreover, our theoretical prediction for the quality factor
of coherent charge oscillations based on phonon decoherence
are higher than the values recently observed experimentally.
This allows us to conclude that phonons are not the primary
source of decoherence in double quantum dot
qubits.},
Doi = {10.1117/12.603649},
Key = {fds245063}
}
@article{Kaul06_Kspect,
Author = {Kaul, RK and Zaránd, G and Chandrasekharan, S and Ullmo, D and Baranger, HU},
Title = {Spectroscopy of the Kondo Problem in a Box},
Journal = {Phys.Rev.Lett.},
Volume = {96},
Number = {17},
Pages = {176802},
Year = {2006},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/16712322},
Abstract = {Motivated by experiments on double quantum dots, we study
the problem of a single magnetic impurity confined in a
finite metallic host. We prove an exact theorem for the
ground state spin, and use analytic and numerical arguments
to map out the spin structure of the excitation spectrum of
the many-body Kondo-correlated state, throughout the weak to
strong coupling crossover. These excitations can be probed
in a simple tunneling-spectroscopy transport experiment; for
that situation we solve rate equations for the
conductance.},
Doi = {10.1103/physrevlett.96.176802},
Key = {Kaul06_Kspect}
}
@article{Priyadarshee06_hcbosons1,
Author = {Priyadarshee, A and Chandrasekharan, S and Lee, JW and Baranger,
HU},
Title = {Quantum Phase Transitions of Hard-Core Bosons in Background
Potentials},
Journal = {Phys. Rev. Lett.},
Volume = {97},
Number = {11},
Pages = {115703},
Year = {2006},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/17025902},
Abstract = {We study the zero temperature phase diagram of hard-core
bosons in two dimensions subjected to three types of
background potentials: staggered, uniform, and random. In
all three cases there is a quantum phase transition from a
superfluid (at small potential) to a normal phase (at large
potential), but with different universality classes. As
expected, the staggered case belongs to the XY universality,
while the uniform potential induces a mean field transition.
The disorder driven transition is clearly different from
both; in particular, we find z approximately 1.4, nu
approximately 1, and beta approximately 0.6.},
Doi = {10.1103/physrevlett.97.115703},
Key = {Priyadarshee06_hcbosons1}
}
@article{Liu05_CoRectifier,
Author = {Liu, R and Ke, S-H and Yang, W and Baranger, HU},
Title = {Organometallic molecular rectification.},
Journal = {The Journal of chemical physics},
Volume = {124},
Number = {2},
Pages = {024718},
Year = {2006},
Month = {January},
ISSN = {0021-9606},
url = {http://www.ncbi.nlm.nih.gov/pubmed/16422637},
Abstract = {We study the rectification of current through a single
molecule with an intrinsic spatial asymmetry. The molecule
contains a cobaltocene moiety in order to take advantage of
its relatively localized and high-energy d states. A
rectifier with large voltage range, high current, and low
threshold can be realized. The evolution of molecular
orbitals under both forward and reverse biases is captured
in a self-consistent nonequilibrium Green function plus
density functional theory description. Our calculations
demonstrate the plausibility of making excellent molecular
diodes by using metallocenes, pointing to a fruitful class
of molecules.},
Doi = {10.1063/1.2141955},
Key = {Liu05_CoRectifier}
}
@article{Ke05_nanotubemetal,
Author = {Ke, S-H and Yang, W and Baranger, HU},
Title = {Nanotube-metal junctions: 2- and 3-terminal electrical
transport.},
Journal = {The Journal of chemical physics},
Volume = {124},
Number = {18},
Pages = {181102},
Year = {2006},
Month = {May},
ISSN = {0021-9606},
url = {http://www.ncbi.nlm.nih.gov/pubmed/16709090},
Abstract = {We address the quality of electrical contact between carbon
nanotubes and metallic electrodes by performing
first-principles calculations for the electron transmission
through ideal 2- and 3-terminal junctions, thus revealing
the physical limit of tube-metal conduction. The structural
model constructed involves surrounding the tube by the metal
atoms of the electrode as in most experiments; we consider
metallic (5,5) and n-doped semiconducting (10,0) tubes
surrounded by Au or Pd. In the case of metallic tubes, the
contact conductance is shown to approach the ideal 4e2/h in
the limit of large contact area. For three-terminals, the
division of flux among the different transmission channels
depends strongly on the metal material. A Pd electrode has
nearly perfect tube-electrode transmission and therefore
turns off the straight transport along the tube. Our results
are in good agreement with some recent experimental reports
and clarify a fundamental discrepancy between theory and
experiment.},
Doi = {10.1063/1.2200356},
Key = {Ke05_nanotubemetal}
}
@article{Liu05_CoNDR,
Author = {Liu, R and Ke, S-H and Baranger, HU and Yang, W},
Title = {Negative differential resistance and hysteresis through an
organometallic molecule from molecular-level
crossing.},
Journal = {Journal of the American Chemical Society},
Volume = {128},
Number = {19},
Pages = {6274-6275},
Year = {2006},
Month = {May},
ISSN = {0002-7863},
url = {http://www.ncbi.nlm.nih.gov/pubmed/16683765},
Abstract = {Analogous to a quantum double-dot system, diblock structured
molecules could also show negative differential resistance
(NDR). Using combined density functional theory and
nonequilibrium Green function technique, we show that
molecular-level crossing in a molecular double-dot system
containing cobaltocene and ferrocene leads to NDR and
hysteresis.},
Doi = {10.1021/ja057054z},
Key = {Liu05_CoNDR}
}
@article{Ghosal05_circdot1,
Author = {Ghosal, A and Güçlü, AD and Umrigar, CJ and Ullmo, D and Baranger,
HU},
Title = {Correlation-induced inhomogeneity in circular quantum
dots},
Journal = {Nature Physics},
Volume = {2},
Number = {5},
Pages = {336-340},
Publisher = {Springer Nature},
Year = {2006},
Month = {May},
ISSN = {1745-2473},
url = {http://www.phy.duke.edu/research/cm/bg/paper/GhosalGUUB06_circdots1.pdf},
Doi = {10.1038/nphys293},
Key = {Ghosal05_circdot1}
}
@article{Novais05_qec1,
Author = {Novais, E and Baranger, HU},
Title = {Decoherence by correlated noise and quantum error
correction.},
Journal = {Physical review letters},
Volume = {97},
Number = {4},
Pages = {040501},
Year = {2006},
Month = {July},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/16907555},
Abstract = {We study the decoherence of a quantum computer in an
environment which is inherently correlated in time and
space. We first derive the nonunitary time evolution of the
computer and environment in the presence of a stabilizer
error correction code, providing a general way to quantify
decoherence for a quantum computer. The general theory is
then applied to the spin-boson model. Our results
demonstrate that effects of long-range correlations can be
systematically reduced by small changes in the error
correction codes.},
Doi = {10.1103/physrevlett.97.040501},
Key = {Novais05_qec1}
}
@article{fds245067,
Author = {Ke, SH and Baranger, HU and Yang, W},
Title = {Development of ab initio calculation for electron transport
and the effects of lead and contact structures in molecular
electronics},
Journal = {Journal of Computational and Theoretical
Nanoscience},
Volume = {3},
Number = {5},
Pages = {819-823},
Publisher = {American Scientific Publishers},
Year = {2006},
Month = {December},
ISSN = {1546-1955},
url = {http://dx.doi.org/10.1166/jctn.2006.022},
Abstract = {A fully self-consistent method combining density functional
theory (DFT) and nonequilibrium Green function approach for
calculating electron transport through molecular devices is
reviewed. It uses periodic boundary conditions for DFT and
treats the leads and molecule of a device system on the same
footing. Also reviewed is its application for the molecular
conductance of Au-benzenedithiol-Au systems. Two important
issues in molecular electronics are discussed: (1) quantum
confinement effects in thin electrodes (leads) and (2)
effects of local atomic configuration around the contacts.
Quantum-confinement- induced waveguide effect causes large
oscillations in the transmission function. Single or double
apex Au atoms at each contact lead to a significant
conductance resonance, which is quite similar to increasing
the molecule-lead separation. Copyright © 2006 American
Scientific Publishers All rights reserved.},
Doi = {10.1166/jctn.2006.022},
Key = {fds245067}
}
@article{fds318399,
Author = {Novais, E and Mucciolo, ER and Baranger, HU},
Title = {Hamiltonian Formulation of Quantum Error Correction and
Correlated Noise},
Journal = {CoRR},
Volume = {abs/0710.1624},
Year = {2007},
Key = {fds318399}
}
@article{fds340249,
Author = {Lee, JW and Chandrasekharan, S and Baranger, HU},
Title = {Disorder-Induced Superfluidity in Hardcore Bosons in Two
Dimensions},
Journal = {Phys. Rev. B},
Year = {2007},
Key = {fds340249}
}
@article{Novais06_qec2,
Author = {Novais, E and Mucciolo, ER and Baranger, HU},
Title = {Resilient quantum computation in correlated environments: a
quantum phase transition perspective.},
Journal = {Physical review letters},
Volume = {98},
Number = {4},
Pages = {040501},
Year = {2007},
Month = {January},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/17358749},
Abstract = {We analyze the problem of a quantum computer in a correlated
environment protected from decoherence by quantum error
correction using a perturbative renormalization group
approach. The scaling equation obtained reflects the
competition between the dimension of the computer and the
scaling dimension of the correlations. For an irrelevant
flow, the error probability is reduced to a stochastic form
for a long time and/or a large number of qubits; thus, the
traditional derivation of the threshold theorem holds for
these error models. In this way, the "threshold theorem" of
quantum computing is rephrased as a dimensional
criterion.},
Doi = {10.1103/physrevlett.98.040501},
Key = {Novais06_qec2}
}
@article{Ke06_oep,
Author = {Ke, S-H and Baranger, HU and Yang, W},
Title = {Role of the exchange-correlation potential in ab initio
electron transport calculations.},
Journal = {The Journal of chemical physics},
Volume = {126},
Number = {20},
Pages = {201102},
Year = {2007},
Month = {May},
ISSN = {0021-9606},
url = {http://www.ncbi.nlm.nih.gov/pubmed/17552745},
Abstract = {The effect of the exchange-correlation potential in ab
initio electron transport calculations is investigated by
constructing optimized effective potentials using different
energy functionals or the electron density from second-order
perturbation theory. The authors calculate electron
transmission through two atomic chain systems, one with
charge transfer and one without. Dramatic effects are caused
by two factors: changes in the energy gap and the
self-interaction error. The error in conductance caused by
the former is about one order of magnitude while that caused
by the latter ranges from several times to two orders of
magnitude, depending on the coupling strength and charge
transfer. The implications for accurate quantum transport
calculations are discussed.},
Doi = {10.1063/1.2743004},
Key = {Ke06_oep}
}
@article{fds245102,
Author = {Ghosal, A and Güçlü, AD and Umrigar, CJ and Ullmo, D and Baranger,
HU},
Title = {Incipient Wigner localization in circular quantum
dots},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {76},
Number = {8},
Pages = {085341},
Publisher = {American Physical Society (APS)},
Year = {2007},
Month = {August},
ISSN = {1098-0121},
url = {http://www.phy.duke.edu/research/cm/bg/paper/GhosalGUUB06_circdots2.pdf},
Abstract = {We study the development of electron-electron correlations
in circular quantum dots as the density is decreased. We
consider a wide range of both electron number, N≤20, and
electron gas parameter, rs 18, using the diffusion quantum
Monte Carlo technique. Features associated with correlation
appear to develop very differently in quantum dots than in
bulk. The main reason is that translational symmetry is
necessarily broken in a dot, leading to density modulation
and inhomogeneity. Electron-electron interactions act to
enhance this modulation ultimately leading to localization.
This process appears to be completely smooth and occurs over
a wide range of density. Thus there is a broad regime of
"incipient" Wigner crystallization in these quantum dots.
Our specific conclusions are (i) the density develops sharp
rings while the pair density shows both radial and angular
inhomogeneity; (ii) the spin of the ground state is
consistent with Hund's (first) rule throughout our entire
range of rs for all 4≤N≤20; (iii) the addition energy
curve first becomes smoother as interactions strengthen-the
mesoscopic fluctuations are damped by correlation-and then
starts to show features characteristic of the classical
addition energy; (iv) localization effects are stronger for
a smaller number of electrons; (v) finally, the gap to
certain spin excitations becomes small at the strong
interaction (large rs) side of our regime. © 2007 The
American Physical Society.},
Doi = {10.1103/PhysRevB.76.085341},
Key = {fds245102}
}
@article{fds245099,
Author = {Ke, S-H and Baranger, HU and Yang, W},
Title = {Electron transport through single conjugated organic
molecules: basis set effects in ab initio
calculations.},
Journal = {The Journal of chemical physics},
Volume = {127},
Number = {14},
Pages = {144107},
Year = {2007},
Month = {October},
ISSN = {0021-9606},
url = {http://www.ncbi.nlm.nih.gov/pubmed/17935386},
Abstract = {We investigate electron transport through single conjugated
molecules--including benzenedithiol, oligophenylene
ethynylenes of different lengths, and a ferrocene-containing
molecule sandwiched between two gold electrodes with
different contact structures--by using a single-particle
Green function method combined with density functional
theory calculation. We focus on the effect of the basis set
in the ab initio calculation. It is shown that the position
of the Fermi energy in the transport gap is sensitive to the
molecule-lead charge transfer which is affected by the size
of basis set. This can dramatically change, by orders of
magnitude, the conductance for long molecules, though the
effect is only minor for short ones. A resonance around the
Fermi energy tends to pin the position of the Fermi energy
and suppress this effect. The result is discussed in
comparison with experimental data.},
Doi = {10.1063/1.2770718},
Key = {fds245099}
}
@article{fds245100,
Author = {Liu, R and Ke, S-H and Yang, W and Baranger, HU},
Title = {Cobaltocene as a spin filter.},
Journal = {The Journal of chemical physics},
Volume = {127},
Number = {14},
Pages = {141104},
Year = {2007},
Month = {October},
ISSN = {0021-9606},
url = {http://www.ncbi.nlm.nih.gov/pubmed/17935378},
Abstract = {In the context of investigating organic molecules for
molecular electronics, doping molecular wires with
transition metal atoms provides additional means of
controlling their transport behavior. The incorporation of
transition metal atoms may generate spin dependence because
the conduction channels of only one spin component align
with the chemical potential of the leads, resulting in a
spin polarized electric current. The possibility to create
such a spin polarized current is investigated here with the
organometallic moiety cobaltocene. According to our
calculations, cobaltocene contacted with gold electrodes
acts as a robust spin filter: Applying a voltage less than
0.2 V causes the current of one spin component crossing the
molecular bridge to be two orders of magnitude larger than
the other. We address the key issue of sensitivity to
molecule-lead geometry by showing that a weak barrier
generated by CH(2) groups between the cobaltocene and the
leads is crucial in reducing the sensitivity to the contact
geometry while only reducing the current modestly. These
results suggest cobaltocene as a robust basic building block
for molecular spintronics.},
Doi = {10.1063/1.2796151},
Key = {fds245100}
}
@article{fds245101,
Author = {Ke, S-H and Baranger, HU and Yang, W},
Title = {Contact transparency of nanotube-molecule-nanotube
junctions.},
Journal = {Physical review letters},
Volume = {99},
Number = {14},
Pages = {146802},
Year = {2007},
Month = {October},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/17930697},
Abstract = {The transparency of contacts between conjugated molecules
and metallic single-walled carbon nanotubes is investigated
using a single-particle Green's function method which
combines a Landauer approach with ab initio density
functional theory. We find that the overall conjugation
required for good contact transparency is broken by
connecting through a six-member ring on the tube. Full
conjugation achieved by an all-carbon contact through a
five-member ring leads to near perfect contact transparency
for different conjugated molecular bridges.},
Doi = {10.1103/physrevlett.99.146802},
Key = {fds245101}
}
@article{fds245098,
Author = {Herman, D and Ong, TT and Usaj, G and Mathur, H and Baranger,
HU},
Title = {Level spacings in random matrix theory and Coulomb blockade
peaks in quantum dots},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {76},
Number = {19},
Pages = {195448},
Publisher = {American Physical Society (APS)},
Year = {2007},
Month = {November},
ISSN = {1098-0121},
url = {http://www.phy.duke.edu/research/cm/bg/paper/HermanOUMB07_rmtCB.pdf},
Abstract = {We obtain analytic formulas for the spacing between
conductance peaks in the Coulomb blockade regime based on
the universal Hamiltonian model of quantum dots. Random
matrix theory results are developed in order to treat
correlations between two and three consecutive spacings in
the energy level spectrum. These are generalizations of the
Wigner surmise for the probability distribution of single
level spacing. The analytic formulas are shown to be in good
agreement with numerical evaluation. © 2007 The American
Physical Society.},
Doi = {10.1103/PhysRevB.76.195448},
Key = {fds245098}
}
@article{fds245094,
Author = {Hentschel, M and Valente, DCB and Mucciolo, ER and Baranger,
HU},
Title = {Improving intrinsic decoherence in multiple-quantum-dot
charge qubits},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {76},
Number = {23},
Pages = {235309},
Publisher = {American Physical Society (APS)},
Year = {2007},
Month = {December},
ISSN = {1098-0121},
url = {http://www.phy.duke.edu/research/cm/bg/paper/HentschelVMB07_3dotqubit.pdf},
Abstract = {We discuss decoherence in charge qubits formed by multiple
lateral quantum dots in the framework of the spin-boson
model and the Born-Markov approximation. We consider the
intrinsic decoherence caused by the coupling to bulk phonon
modes. Two distinct quantum dot configurations are studied:
(i) Three quantum dots in a ring geometry with one excess
electron in total and (ii) arrays of quantum dots where the
computational basis states form multipole charge
configurations. For the three-dot qubit, we demonstrate the
possibility of performing one- and two-qubit operations by
solely tuning gate voltages. Compared to a previous proposal
involving a linear three-dot spin qubit, the three-dot
charge qubit allows for less overhead on two-qubit
operations. For small interdot tunnel amplitudes, the
three-dot qubits have Q factors much higher than those
obtained for double-dot systems. The high-multipole dot
configurations also show a substantial decrease in
decoherence at low operation frequencies when compared to
the double-dot qubit. © 2007 The American Physical
Society.},
Doi = {10.1103/PhysRevB.76.235309},
Key = {fds245094}
}
@article{fds245093,
Author = {Hentschel, M and Ullmo, D and Baranger, HU},
Title = {Fermi edge singularities in the mesoscopic regime:
Photoabsorption spectra},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {76},
Number = {24},
Pages = {245419},
Publisher = {American Physical Society (APS)},
Year = {2007},
Month = {December},
ISSN = {1098-0121},
url = {http://www.phy.duke.edu/research/cm/bg/paper/HentschelUB07_mesfes2.pdf},
Abstract = {We study Fermi edge singularities in photoabsorption spectra
of generic mesoscopic systems such as quantum dots or
nanoparticles. We predict deviations from
macroscopic-metallic behavior and propose experimental
setups for the observation of these effects. The theory is
based on the model of a localized, or rank one, perturbation
caused by the (core) hole left behind after the
photoexcitation of an electron into the conduction band. The
photoabsorption spectra result from the competition between
two many-body responses, Anderson's orthogonality
catastrophe and the Mahan-Nozières-DeDominicis
contribution. Both mechanisms depend on the system size
through the number of particles and, more importantly,
fluctuations produced by the coherence characteristic of
mesoscopic samples. The latter lead to a modification of the
dipole matrix element and trigger one of our key results: a
rounded K -edge typically found in metals will turn into a
(slightly) peaked edge on average in the mesoscopic regime.
We consider in detail the effect of the "bound state"
produced by the core hole. © 2007 The American Physical
Society.},
Doi = {10.1103/PhysRevB.76.245419},
Key = {fds245093}
}
@article{fds245092,
Author = {Güçlü, AD and Ghosal, A and Umrigar, CJ and Baranger,
HU},
Title = {Interaction-induced strong localization in quantum
dots},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {77},
Number = {4},
Pages = {041301(R)},
Publisher = {American Physical Society (APS)},
Year = {2008},
Month = {January},
ISSN = {1098-0121},
url = {http://www.phy.duke.edu/research/cm/bg/paper/GucluGUB07_stronglocdots.pdf},
Abstract = {We argue that Coulomb blockade phenomena are a useful probe
of the crossover to strong correlation in quantum dots.
Through calculations at low density using variational and
diffusion quantum Monte Carlo (up to rs ∼55), we find that
the addition energy shows a clear progression from features
associated with shell structure to those caused by
commensurability of a Wigner crystal. This crossover (which
occurs near rs ∼20 for spin-polarized electrons) is, then,
a signature of interaction-driven localization. As the
addition energy is directly measurable in Coulomb blockade
conductance experiments, this provides a direct probe of
localization in the low density electron gas. © 2008 The
American Physical Society.},
Doi = {10.1103/PhysRevB.77.041301},
Key = {fds245092}
}
@article{fds245091,
Author = {Novais, E and Mucciolo, ER and Baranger, HU},
Title = {Hamiltonian formulation of quantum error correction and
correlated noise: Effects of syndrome extraction in the
long-time limit},
Journal = {Physical Review A - Atomic, Molecular, and Optical
Physics},
Volume = {78},
Number = {1},
Pages = {012314 (18 pages)},
Publisher = {American Physical Society (APS)},
Year = {2008},
Month = {July},
ISSN = {1050-2947},
url = {http://www.phy.duke.edu/research/cm/bg/paper/NovaisBM07_qec3.pdf},
Abstract = {We analyze the long-time behavior of a quantum computer
running a quantum error correction (QEC) code in the
presence of a correlated environment. Starting from a
Hamiltonian formulation of realistic noise models, and
assuming that QEC is indeed possible, we find formal
expressions for the probability of a given syndrome history
and the associated residual decoherence encoded in the
reduced density matrix. Systems with nonzero gate times
("long gates") are included in our analysis by using an
upper bound on the noise. In order to introduce the local
error probability for a qubit, we assume that propagation of
signals through the environment is slower than the QEC
period (hypercube assumption). This allows an explicit
calculation in the case of a generalized spin-boson model
and a quantum frustration model. The key result is a
dimensional criterion: If the correlations decay
sufficiently fast, the system evolves toward a stochastic
error model for which the threshold theorem of
fault-tolerant quantum computation has been proven. On the
other hand, if the correlations decay slowly, the
traditional proof of this threshold theorem does not hold.
This dimensional criterion bears many similarities to
criteria that occur in the theory of quantum phase
transitions. © 2008 The American Physical
Society.},
Doi = {10.1103/PhysRevA.78.012314},
Key = {fds245091}
}
@article{Ke08_qint,
Author = {Ke, S-H and Yang, W and Baranger, HU},
Title = {Quantum-interference-controlled molecular
electronics.},
Journal = {Nano letters},
Volume = {8},
Number = {10},
Pages = {3257-3261},
Year = {2008},
Month = {October},
ISSN = {1530-6984},
url = {http://www.ncbi.nlm.nih.gov/pubmed/18803424},
Abstract = {Quantum interference in coherent transport through single
molecular rings may provide a mechanism to control the
current in molecular electronics. We investigate its
applicability, using a single-particle Green function method
combined with ab initio electronic structure calculations.
We find that the quantum interference effect (QIE) is
strongly dependent on the interaction between molecular
pi-states and contact sigma-states. It is masked by sigma
tunneling in small molecular rings with Au leads, such as
benzene, due to strong pi-sigma hybridization, while it is
preserved in large rings, such as [18]annulene, which then
could be used to realize quantum interference effect (QIE)
transistors.},
Doi = {10.1021/nl8016175},
Key = {Ke08_qint}
}
@article{fds245089,
Author = {Kaul, RK and Ullmo, D and Zarand, G and Chandrasekharan, S and Baranger,
HU},
Title = {Ground state and excitations of quantum dots with magnetic
impurities},
Journal = {Phys. Rev. B},
Volume = {80},
Number = {3},
Pages = {035318},
Publisher = {American Physical Society (APS)},
Year = {2009},
ISSN = {1098-0121},
url = {http://dx.doi.org/10.1103/PhysRevB.80.035318},
Abstract = {We consider an “impurity” with a spin degree of freedom
coupled to a finite reservoir of non-interacting electrons,
a system which may be realized by either a true impurity in
a metallic nano-particle or a small quantum dot coupled to a
large one. We show how the physics of such a spin impurity
is revealed in the many-body spectrum of the entire
finite-size system; in particular, the evolution of the
spectrum with the strength of the impurity-reservoir
coupling reflects the fundamental many-body correlations
present. Explicit calculation in the strong and weak
coupling limits shows that the spectrum and its evolution
are sensitive to the nature of the impurity and the parity
of electrons in the reservoir. The effect of the finite size
spectrum on two experimental observables is considered.
First, we propose an experimental setup in which the
spectrum may be conveniently measured using tunneling
spectroscopy. A rate equation calculation of the
differential conductance suggests how the many-body spectral
features may be observed. Second, the finite-temperature
magnetic susceptibility is presented, both the impurity
susceptibility and the local susceptibility. Extensive
quantum Monte-Carlo calculations show that the local
susceptibility deviates from its bulk scaling form.
Nevertheless, for special assumptions about the reservoir
– the “clean Kondo box” model – we demonstrate that
finite-size scaling is recovered. Explicit numerical
evaluations of these scaling functions are given, both for
even and odd parity and for the canonical and
grand-canonical ensembles.},
Doi = {10.1103/PhysRevB.80.035318},
Key = {fds245089}
}
@article{Ke08_thermopower,
Author = {Ke, SH and Yang, W and Curtarolo, S and Baranger,
HU},
Title = {Thermopower of Molecular Junctions},
Journal = {Nano Lett.},
Volume = {9},
Number = {3},
Pages = {1011-1014},
Year = {2009},
Month = {January},
ISSN = {1530-6984},
url = {http://www.phy.duke.edu/research/cm/bg/paper/KeYCB09_thermopower1.pdf},
Abstract = {Molecular nanojunctions may support efficient thermoelectric
conversion through enhanced thermopower. Recently, this
quantity has been measured for several conjugated molecular
nanojunctions with gold electrodes. Considering the wide
variety of possible metal/molecule systems-almost none of
which have been studied-it seems highly desirable to be able
to calculate the thermopower of junctions with reasonable
accuracy and high efficiency. To address this task, we
demonstrate an effective approach based on the single
particle green function (SPGF) method combined with density
functional theory (DFT) using B3LYP and PBE0 energy
functionals. Systematic good agreement between theory and
experiment is obtained; indeed, much better agreement is
found here than for comparable calculations of the
conductance.},
Doi = {10.1021/nl8031229},
Key = {Ke08_thermopower}
}
@article{Wurm08_graphene,
Author = {Wurm, J and Rycerz, A and Adagideli, I and Wimmer, M and Richter, K and Baranger, HU},
Title = {Symmetry classes in graphene quantum dots: universal
spectral statistics, weak localization, and conductance
fluctuations.},
Journal = {Physical review letters},
Volume = {102},
Number = {5},
Pages = {056806},
Year = {2009},
Month = {February},
ISSN = {0031-9007},
url = {http://www.ncbi.nlm.nih.gov/pubmed/19257538},
Abstract = {We study the symmetry classes of graphene quantum dots, both
open and closed, through the conductance and energy level
statistics. For abrupt termination of the lattice, these
properties are well described by the standard orthogonal and
unitary ensembles. However, for smooth mass confinement,
special time-reversal symmetries associated with the
sublattice and valley degrees of freedom are critical: they
lead to block diagonal Hamiltonians and scattering matrices
with blocks belonging to the unitary symmetry class even at
zero magnetic field. While the effect of this structure is
clearly seen in the conductance of open dots, it is
suppressed in the spectral statistics of closed dots,
because the intervalley scattering time is shorter than the
time required to resolve a level spacing in the closed
systems but longer than the escape time of the open
systems.},
Doi = {10.1103/physrevlett.102.056806},
Key = {Wurm08_graphene}
}
@article{fds304506,
Author = {Ke, S-H and Yang, W and Curtarolo, S and Baranger,
HU},
Title = {Thermopower of molecular junctions: an ab initio
study.},
Journal = {Nano letters},
Volume = {9},
Number = {3},
Pages = {1011-1014},
Year = {2009},
Month = {March},
ISSN = {1530-6984},
url = {http://www.ncbi.nlm.nih.gov/pubmed/19203208},
Abstract = {Molecular nanojunctions may support efficient thermoelectric
conversion through enhanced thermopower. Recently, this
quantity has been measured for several conjugated molecular
nanojunctions with gold electrodes. Considering the wide
variety of possible metal/molecule systems-almost none of
which have been studied-it seems highly desirable to be able
to calculate the thermopower of junctions with reasonable
accuracy and high efficiency. To address this task, we
demonstrate an effective approach based on the single
particle green function (SPGF) method combined with density
functional theory (DFT) using B3LYP and PBE0 energy
functionals. Systematic good agreement between theory and
experiment is obtained; indeed, much better agreement is
found here than for comparable calculations of the
conductance.},
Doi = {10.1021/nl8031229},
Key = {fds304506}
}
@article{Kaul08_Kspect2,
Author = {R. K. Kaul and D. Ullmo and G. Zarand and S. Chandrasekharan and H. U. Baranger},
Title = {Ground State Excitations of Quantum Dots with ``Magnetic
Impurities''},
Journal = {Phys. Rev. B},
Volume = {80},
Pages = {035318},
Year = {2009},
Month = {July},
url = {http://www.phy.duke.edu/research/cm/bg/paper/KaulUZCB09_longkondo.pdf},
Key = {Kaul08_Kspect2}
}
@article{fds245086,
Author = {Wurm, J and Wimmer, M and Adagideli, I and Richter, K and Baranger,
HU},
Title = {Interfaces within graphene nanoribbons},
Journal = {New Journal of Physics},
Volume = {11},
Number = {9},
Pages = {095022-095022},
Publisher = {IOP Publishing},
Year = {2009},
Month = {September},
ISSN = {1367-2630},
url = {http://www.phy.duke.edu/research/cm/bg/paper/WurmWARB09_graphenenanoribbons.pdf},
Abstract = {We study the conductance through two types of graphene
nanostructures: nanoribbon junctions in which the width
changes from wide to narrow, and curved nanoribbons. In the
wide-narrow structures, substantial reflection occurs from
the wide-narrow interface, in contrast to the behavior of
the much studied electron gas waveguides. In the curved
nanoribbons, the conductance is very sensitive to details
such as whether regions of a semiconducting armchair
nanoribbon are included in the curved structure-such regions
strongly suppress the conductance. Surprisingly, this
suppression is not due to the band gap of the semiconducting
nanoribbon, but is linked to the valley degree of freedom.
Although we study these effects in the simplest contexts,
they can be expected to occur for more complicated
structures, and we show results for rings as well. We
conclude that experience from electron gas waveguides does
not carry over to graphene nanostructures. The interior
interfaces causing extra scattering result from the extra
effective degrees of freedom of the graphene structure,
namely the valley and sublattice pseudospins. © IOP
Publishing Ltd and Deutsche Physikalische
Gesellschaft.},
Doi = {10.1088/1367-2630/11/9/095022},
Key = {fds245086}
}
@article{Guclu08_inhomowire,
Author = {Güçlü, AD and Umrigar, CJ and Jiang, H and Baranger,
HU},
Title = {Localization in an inhomogeneous quantum
wire},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {80},
Number = {20},
Pages = {201302(R)},
Publisher = {American Physical Society (APS)},
Year = {2009},
Month = {November},
ISSN = {1098-0121},
url = {http://www.phy.duke.edu/research/cm/bg/paper/GucluUJB08_inhomoqwire.pdf},
Abstract = {We study interaction-induced localization of electrons in an
inhomogeneous quasi-one-dimensional system-a wire with two
regions, one at low density and the other high. Quantum
Monte Carlo techniques are used to treat the strong Coulomb
interactions in the low-density region, where localization
of electrons occurs. The nature of the transition from high
to low density depends on the density gradient-if it is
steep, a barrier develops between the two regions, causing
Coulomb blockade effects. Ferromagnetic spin polarization
does not appear for any parameters studied. The picture
emerging is in good agreement with measurements of tunneling
between wires. © 2009 The American Physical
Society.},
Doi = {10.1103/PhysRevB.80.201302},
Key = {Guclu08_inhomowire}
}
@article{Dong10_4dotsqpt,
Author = {Liu, D and Chandrasekharan, S and Baranger, HU},
Title = {Quantum Phase Transition and Dynamically Enhanced Symmetry
in Quadruple Quantum Dot System},
Journal = {Physical Review Letters},
Volume = {105},
Number = {25},
Pages = {256801},
Year = {2010},
url = {http://www.ncbi.nlm.nih.gov/pubmed/21231607},
Abstract = {We propose a system of four quantum dots designed to study
the competition between three types of interactions:
Heisenberg, Kondo, and Ising. We find a rich phase diagram
containing two sharp features: a quantum phase transition
(QPT) between charge-ordered and charge-liquid phases and a
dramatic resonance in the charge liquid visible in the
conductance. The QPT is of the Kosterlitz-Thouless type with
a discontinuous jump in the conductance at the transition.
We connect the resonance phenomenon with the degeneracy of
three levels in the isolated quadruple dot and argue that
this leads to a Kondo-like emergent symmetry from left-right
Z2 to U(1).},
Doi = {10.1103/physrevlett.105.256801},
Key = {Dong10_4dotsqpt}
}
@article{Dong10_conductance,
Author = {Liu, D and Chandrasekharan, S and Baranger, HU},
Title = {Conductance of quantum impurity models from quantum Monte
Carlo},
Journal = {Physical Review B},
Volume = {82},
Number = {16},
Pages = {165447},
Publisher = {American Physical Society (APS)},
Year = {2010},
ISSN = {1098-0121},
url = {http://hdl.handle.net/10161/4258 Duke open
access},
Abstract = {The conductance of two Anderson impurity models, one with
twofold and another with fourfold degeneracy, representing
two types of quantum dots, is calculated using a world-line
quantum Monte Carlo (QMC) method. Extrapolation of the
imaginary time QMC data to zero frequency yields the linear
conductance, which is then compared to numerical
renormalization-group results in order to assess its
accuracy. We find that the method gives excellent results at
low temperature (T TK) throughout the mixed-valence and
Kondo regimes but it is unreliable for higher temperature.
© 2010 The American Physical Society.},
Doi = {10.1103/PhysRevB.82.165447},
Key = {Dong10_conductance}
}
@article{fds245084,
Author = {Wurm, J and Wimmer, M and Baranger, HU and Richter,
K},
Title = {Graphene rings in magnetic fields: Aharonov-Bohm effect and
valley splitting},
Journal = {Semiconductor Science and Technology},
Volume = {25},
Number = {3},
Pages = {034003-034003},
Publisher = {IOP Publishing},
Year = {2010},
Month = {February},
ISSN = {0268-1242},
url = {http://www.phy.duke.edu/research/cm/bg/paper/WurmWBR09_graphenerings.pdf},
Abstract = {We study the conductance of mesoscopic graphene rings in the
presence of a perpendicular magnetic field by means of
numerical calculations based on a tight-binding model.
First, we consider the magnetoconductance of such rings and
observe the Aharonov-Bohm effect. We investigate different
regimes of the magnetic flux up to the quantum Hall regime,
where the Aharonov-Bohm oscillations are suppressed. Results
for both clean (ballistic) and disordered (diffusive) rings
are presented. Second, we study rings with smooth mass
boundary that are weakly coupled to leads. We show that the
valley degeneracy of the eigenstates in closed graphene
rings can be lifted by a small magnetic flux, and that this
lifting can be observed in the transport properties of the
system. © 2010 IOP Publishing Ltd.},
Doi = {10.1088/0268-1242/25/3/034003},
Key = {fds245084}
}
@article{Ke10_timedep,
Author = {Ke, SH and Liu, R and Yang, W and Baranger, HU},
Title = {Time-Dependent Transport Through Molecular
Junctions},
Journal = {J. Chem. Phys.},
Volume = {132},
Number = {23},
Pages = {234105},
Year = {2010},
Month = {June},
url = {http://www.ncbi.nlm.nih.gov/pubmed/20572687},
Abstract = {We investigate transport properties of molecular junctions
under two types of bias--a short time pulse or an ac
bias--by combining a solution for Green's functions in the
time domain with electronic structure information coming
from ab initio density functional calculations. We find that
the short time response depends on lead structure, bias
voltage, and barrier heights both at the molecule-lead
contacts and within molecules. Under a low frequency ac
bias, the electron flow either tracks or leads the bias
signal (resistive or capacitive response) depending on
whether the junction is perfectly conducting or not. For
high frequency, the current lags the bias signal due to the
kinetic inductance. The transition frequency is an intrinsic
property of the junctions.},
Doi = {10.1063/1.3435351},
Key = {Ke10_timedep}
}
@article{Novais10_howlong,
Author = {Novais, E and Mucciolo, ER and Baranger, HU},
Title = {Bound on quantum computation time: Quantum error correction
in a critical environment},
Journal = {Physical Review A - Atomic, Molecular, and Optical
Physics},
Volume = {82},
Number = {2},
Pages = {020303(R)},
Publisher = {American Physical Society (APS)},
Year = {2010},
Month = {August},
ISSN = {1050-2947},
url = {http://hdl.handle.net/10161/3348 Duke open
access},
Abstract = {We obtain an upper bound on the time available for quantum
computation for a given quantum computer and decohering
environment with quantum error correction implemented.
First, we derive an explicit quantum evolution operator for
the logical qubits and show that it has the same form as
that for the physical qubits but with a reduced coupling
strength to the environment. Using this evolution operator,
we find the trace distance between the real and ideal states
of the logical qubits in two cases. For a super-Ohmic bath,
the trace distance saturates, while for Ohmic or sub-Ohmic
baths, there is a finite time before the trace distance
exceeds a value set by the user. © 2010 The American
Physical Society.},
Doi = {10.1103/PhysRevA.82.020303},
Key = {Novais10_howlong}
}
@article{Gleb10_kondobox,
Author = {Bomze, Y and Borzenets, I and Mebrahtu, H and Makarovski, A and Baranger, HU and Finkelstein, G},
Title = {Two-stage Kondo effect and Kondo-box level spectroscopy in a
carbon nanotube},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {82},
Number = {16},
Pages = {161411(R)},
Publisher = {American Physical Society (APS)},
Year = {2010},
Month = {October},
ISSN = {1098-0121},
url = {http://hdl.handle.net/10161/4257 Duke open
access},
Abstract = {The concept of the "Kondo box" describes a single spin,
antiferromagnetically coupled to a quantum dot with a finite
level spacing. Here, a Kondo box is formed in a carbon
nanotube interacting with a localized electron. We
investigate the spins of its first few eigenstates and
compare them to a recent theory. In an "open" Kondo-box,
strongly coupled to the leads, we observe a nonmonotonic
temperature dependence of the nanotube conductance, which
results from a competition between the Kondo-box singlet and
the "conventional" Kondo state that couples the nanotube to
the leads. © 2010 The American Physical
Society.},
Doi = {10.1103/PhysRevB.82.161411},
Key = {Gleb10_kondobox}
}
@article{Huaixiu10_1TLS,
Author = {Zheng, H and Gauthier, DJ and Baranger, HU},
Title = {Waveguide QED: Many-body bound-state effects in coherent and
Fock-state scattering from a two-level system},
Journal = {Physical Review A - Atomic, Molecular, and Optical
Physics},
Volume = {82},
Number = {6},
Pages = {063816},
Publisher = {American Physical Society (APS)},
Year = {2010},
Month = {December},
ISSN = {1050-2947},
url = {http://hdl.handle.net/10161/8974 Duke open
access},
Abstract = {Strong coupling between a two-level system (TLS) and bosonic
modes produces dramatic quantum optics effects. We consider
a one-dimensional continuum of bosons coupled to a single
localized TLS, a system which may be realized in a variety
of plasmonic, photonic, or electronic contexts. We present
the exact many-body scattering eigenstate obtained by
imposing open boundary conditions. Multiphoton bound states
appear in the scattering of two or more photons due to the
coupling between the photons and the TLS. Such bound states
are shown to have a large effect on scattering of both Fock-
and coherent-state wave packets, especially in the
intermediate coupling-strength regime. We compare the
statistics of the transmitted light with a coherent state
having the same mean photon number: as the interaction
strength increases, the one-photon probability is suppressed
rapidly, and the two- and three-photon probabilities are
greatly enhanced due to the many-body bound states. This
results in non-Poissonian light. © 2010 The American
Physical Society.},
Doi = {10.1103/PhysRevA.82.063816},
Key = {Huaixiu10_1TLS}
}
@article{fds245074,
Author = {Ullmo, D and Burdin, S and Liu, DE and Baranger, HU},
Title = {Kondo effect and mesoscopic fluctuations},
Journal = {Pramana - Journal of Physics},
Volume = {77},
Number = {5},
Pages = {769-779},
Publisher = {Springer Nature America, Inc},
Year = {2011},
Month = {November},
ISSN = {0304-4289},
url = {http://dx.doi.org/10.1007/s12043-011-0191-3},
Abstract = {Two important themes in nanoscale physics in the last two
decades are correlations between electrons and mesoscopic
fluctuations. Here we review our recent work on the
intersection of these two themes. The setting is the Kondo
effect, a paradigmatic example of correlated electron
physics, in a nanoscale system with mesoscopic fluctuations;
in particular, we consider a small quantum dot coupled to a
finite reservoir (which itself may be a large quantum dot).
We discuss three aspects of this problem. First, in the
high-temperature regime, we argue that a Kondo temperature
TK which takes into account the mesoscopic fluctuations is a
relevant concept: for instance, physical properties are
universal functions of T/TK. Secondly, when the temperature
is much less than the mean level spacing due to confinement,
we characterize a natural cross-over from weak to strong
coupling. This strong coupling regime is itself
characterized by well-defined single-particle levels, as one
can see from a Nozières Fermi-liquid theory argument.
Finally, using a mean-field technique, we connect the
mesoscopic fluctuations of the quasiparticles in the weak
coupling regime to those at strong coupling. © Indian
Academy of Sciences.},
Doi = {10.1007/s12043-011-0191-3},
Key = {fds245074}
}
@article{Dong11_majoranadetect,
Author = {Liu, DE and Baranger, HU},
Title = {Detecting a Majorana-fermion zero mode using a quantum
dot},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {84},
Number = {20},
Pages = {201308(R)},
Publisher = {American Physical Society (APS)},
Year = {2011},
Month = {November},
ISSN = {1098-0121},
url = {http://www.phy.duke.edu/research/cm/bg/paper/LiuB11_majoranadetect.pdf},
Abstract = {We propose an experimental setup for detecting a Majorana
zero mode consisting of a spinless quantum dot coupled to
the end of a p-wave superconducting nanowire. The Majorana
bound state at the end of the wire strongly influences the
conductance through the quantum dot: Driving the wire
through the topological phase transition causes a sharp jump
in the conductance by a factor of 1/2. In the topological
phase, the zero-temperature peak value of the dot
conductance (i.e., when the dot is on resonance and
symmetrically coupled to the leads) is e2/2h. In contrast,
if the wire is in its trivial phase, the conductance peak
value is e2/h, or if a regular fermionic zero mode occurs on
the end of the wire, the conductance is 0. The system can
also be used to tune Flensberg's qubit system to the
required degeneracy point. © 2011 American Physical
Society.},
Doi = {10.1103/PhysRevB.84.201308},
Key = {Dong11_majoranadetect}
}
@article{Huaixiu11_4LS,
Author = {Zheng, H and Gauthier, DJ and Baranger, HU},
Title = {Cavity-free photon blockade induced by many-body bound
States},
Journal = {Physical Review Letters},
Volume = {107},
Number = {22},
Pages = {223601},
Year = {2011},
Month = {November},
url = {http://www.ncbi.nlm.nih.gov/pubmed/22182028},
Abstract = {The manipulation of individual, mobile quanta is a key goal
of quantum communication; to achieve this, nonlinear
phenomena in open systems can play a critical role. We show
theoretically that a variety of strong quantum nonlinear
phenomena occur in a completely open one-dimensional
waveguide coupled to an N-type four-level system. We focus
on photon blockade and the creation of single-photon states
in the absence of a cavity. Many-body bound states appear
due to the strong photon-photon correlation mediated by the
four-level system. These bound states cause photon blockade,
which can generate a sub-Poissonian single-photon source. ©
2011 American Physical Society.},
Doi = {10.1103/PhysRevLett.107.223601},
Key = {Huaixiu11_4LS}
}
@article{fds245075,
Author = {Liu, DE and Burdin, S and Baranger, HU and Ullmo,
D},
Title = {From weak- to strong-coupling mesoscopic Fermi
liquids},
Journal = {EPL},
Volume = {97},
Number = {1},
Pages = {17006-17006},
Publisher = {IOP Publishing},
Year = {2012},
Month = {January},
ISSN = {0295-5075},
url = {http://www.phy.duke.edu/research/cm/bg/paper/LiuBBU11_weaktostrong.pdf},
Abstract = {We study mesoscopic fluctuations in a system in which there
is a continuous connection between two distinct Fermi
liquids, asking whether the mesoscopic variation in the two
limits is correlated. The particular system studied is an
Anderson impurity coupled to a finite mesoscopic reservoir
described by the random matrix theory, a structure which can
be realized using quantum dots. We use the slave boson
mean-field approach to connect the levels of the uncoupled
system to those of the strong-coupling Nozières' Fermi
liquid. We find strong but not complete correlation between
the mesoscopic properties in the two limits and several
universal features. © 2012 Europhysics Letters
Association.},
Doi = {10.1209/0295-5075/97/17006},
Key = {fds245075}
}
@article{fds245072,
Author = {Zheng, H and Gauthier, DJ and Baranger, HU},
Title = {Strongly correlated photons generated by coupling a three-
or four-level system to a waveguide},
Journal = {Physical Review A - Atomic, Molecular, and Optical
Physics},
Volume = {85},
Number = {4},
Pages = {043832},
Publisher = {American Physical Society (APS)},
Year = {2012},
Month = {April},
ISSN = {1050-2947},
url = {http://www.phy.duke.edu/research/cm/bg/paper/ZhengGB12_strongcor3LS4LS.pdf},
Abstract = {We study the generation of strongly correlated photons by
coupling an atom to photonic quantum fields in a
one-dimensional waveguide. Specifically, we consider a
three-level or four-level system for the atom. Photon-photon
bound states emerge as a manifestation of the strong
photon-photon correlation mediated by the atom. Effective
repulsive or attractive interaction between photons can be
produced, causing either suppressed multiphoton transmission
(photon blockade) or enhanced multiphoton transmission
(photon-induced tunneling). As a result, nonclassical light
sources can be generated on demand by sending coherent
states into the proposed system. We calculate the
second-order correlation function of the transmitted field
and observe bunching and antibunching caused by the bound
states. Furthermore, we demonstrate that the proposed system
can produce photon pairs with a high degree of spectral
entanglement, which have a large capacity for carrying
information and are important for large-alphabet quantum
communication. © 2012 American Physical
Society.},
Doi = {10.1103/PhysRevA.85.043832},
Key = {fds245072}
}
@article{fds245071,
Author = {Liu, DE and Burdin, S and Baranger, HU and Ullmo,
D},
Title = {Mesoscopic Anderson box: Connecting weak to strong
coupling},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {85},
Number = {15},
Pages = {155455},
Publisher = {American Physical Society (APS)},
Year = {2012},
Month = {April},
ISSN = {1098-0121},
url = {http://www.phy.duke.edu/research/cm/bg/paper/LiuBBU12_mesoAndbox.pdf},
Abstract = {We study the Anderson impurity problem in a mesoscopic
setting, namely the "Anderson box," in which the impurity is
coupled to finite reservoir having a discrete spectrum and
large sample-to-sample mesoscopic fluctuations. Note that
both the weakly coupled and strong coupling Anderson
impurity problems are characterized by a Fermi-liquid theory
with weakly interacting quasiparticles. We study how the
statistical fluctuations in these two problems are
connected, using random matrix theory and the slave boson
mean-field approximation (SBMFA). First, for a resonant
level model such as results from the SBMFA, we find the
joint distribution of energy levels with and without the
resonant level present. Second, if only energy levels within
the Kondo resonance are considered, the distributions of
perturbed levels collapse to universal forms for both
orthogonal and unitary ensembles for all values of the
coupling. These universal curves are described well by a
simple Wigner-surmise-type toy model. Third, we study the
fluctuations of the mean-field parameters in the SBMFA,
finding that they are small. Finally, the change in the
intensity of an eigenfunction at an arbitrary point is
studied, such as is relevant in conductance measurements. We
find that the introduction of the strongly coupled impurity
considerably changes the wave function but that a
substantial correlation remains. © 2012 American Physical
Society.},
Doi = {10.1103/PhysRevB.85.155455},
Key = {fds245071}
}
@article{Henok11_RLdissip1,
Author = {Mebrahtu, HT and Borzenets, IV and Liu, DE and Zheng, H and Bomze, YV and Smirnov, AI and Baranger, HU and Finkelstein, G},
Title = {Quantum phase transition in a resonant level coupled to
interacting leads.},
Journal = {Nature},
Volume = {488},
Number = {7409},
Pages = {61-64},
Year = {2012},
Month = {August},
url = {http://www.ncbi.nlm.nih.gov/pubmed/22859201},
Abstract = {A Luttinger liquid is an interacting one-dimensional
electronic system, quite distinct from the 'conventional'
Fermi liquids formed by interacting electrons in two and
three dimensions. Some of the most striking properties of
Luttinger liquids are revealed in the process of electron
tunnelling. For example, as a function of the applied bias
voltage or temperature, the tunnelling current exhibits a
non-trivial power-law suppression. (There is no such
suppression in a conventional Fermi liquid.) Here, using a
carbon nanotube connected to resistive leads, we create a
system that emulates tunnelling in a Luttinger liquid, by
controlling the interaction of the tunnelling electron with
its environment. We further replace a single tunnelling
barrier with a double-barrier, resonant-level structure and
investigate resonant tunnelling between Luttinger liquids.
At low temperatures, we observe perfect transparency of the
resonant level embedded in the interacting environment, and
the width of the resonance tends to zero. We argue that this
behaviour results from many-body physics of interacting
electrons, and signals the presence of a quantum phase
transition. Given that many parameters, including the
interaction strength, can be precisely controlled in our
samples, this is an attractive model system for studying
quantum critical phenomena in general, with wide-reaching
implications for understanding quantum phase transitions in
more complex systems, such as cold atoms and strongly
correlated bulk materials.},
Doi = {10.1038/nature11265},
Key = {Henok11_RLdissip1}
}
@article{fds245045,
Author = {Ullmo, D and Liu, DE and Burdin, S and Baranger, HU},
Title = {Fermi-liquid regime of the mesoscopic Kondo
problem},
Journal = {Eur. Phys. J. B},
Volume = {86},
Number = {8},
Pages = {352},
Publisher = {Springer Science and Business Media LLC},
Year = {2012},
Month = {October},
ISSN = {1434-6028},
url = {http://dx.doi.org/10.1140/epjb/e2013-40418-3},
Abstract = {We consider the low temperature regime of the mesoscopic
Kondo problem, and in particular the relevance of a
Fermi-liquid description of this regime. Using two
complementary approaches -- a mean field slave fermion
approximation on the one hand and a Fermi-liquid description
"\`a la Nozi\`eres" supplemented by an argument of
separation of scale on the other hand -- we show that they
both lead to (essentially) the same quasi-particle spectra,
providing in this way a strong indication that they both
give the correct physics of this regime.},
Doi = {10.1140/epjb/e2013-40418-3},
Key = {fds245045}
}
@article{fds245044,
Author = {Mebrahtu, HT and Borzenets, IV and Zheng, H and Bomze, YV and Smirnov,
AI and Florens, S and Baranger, HU and Finkelstein,
G},
Title = {Observation of majorana quantum critical behaviour in a
resonant level coupled to a dissipative environment},
Journal = {Nature Physics},
Volume = {9},
Number = {11},
Pages = {732-737},
Year = {2013},
Month = {January},
ISSN = {1745-2473},
url = {http://dx.doi.org/10.1038/nphys2735},
Abstract = {A quantum phase transition is an abrupt change between two
distinct ground states of a many-body system, driven by an
external parameter. In the vicinity of the quantum critical
point (QCP) where the transition occurs, a new phase may
emerge that is determined by quantum fluctuations and is
very different from either phase. In particular, a
conducting system may exhibit non-Fermi-liquid behaviour.
Although this scenario is well established theoretically,
controllable experimental realizations are rare. Here, we
experimentally investigate the nature of the QCP in a simple
nanoscale system - a spin-polarized resonant level coupled
to dissipative contacts. We fine-tune the system to the QCP,
realized exactly on-resonance and when the coupling between
the level and the two contacts is symmetric. Several
anomalous transport scaling laws are demonstrated, including
a striking non-Fermi-liquid scattering rate at the QCP,
indicating fractionalization of the resonant level into two
Majorana quasiparticles. © 2013 Macmillan Publishers
Limited.},
Doi = {10.1038/nphys2735},
Key = {fds245044}
}
@article{fds365312,
Author = {Bera, S and Florens, S and Baranger, H and Roch, N and Nazir, A and Chin,
A},
Title = {Unveiling environmental entanglement in strongly dissipative
qubits},
Journal = {arXiv},
Pages = {1301.7430-1301.7430},
Publisher = {arXiv},
Year = {2013},
Month = {January},
Abstract = {The coupling of a qubit to a macroscopic reservoir plays a
fundamental role in understanding the complex transition
from the quantum to the classical world. Considering a
harmonic environment, we use both intuitive arguments and
numerical many-body quantum tomography to study the
structure of the complete wavefunction arising in the
strong-coupling regime, reached for intense
qubit-environment interaction. The resulting
strongly-correlated many-body ground state is built from
quantum superpositions of adiabatic (polaron-like) and
non-adiabatic (antipolaron-like) contributions from the bath
of quantum oscillators. The emerging Schrödinger cat
environmental wavefunctions can be described quantitatively
via simple variational coherent states. In contrast to
qubit-environment entanglement, we show that
non-classicality and entanglement among the modes in the
reservoir are crucial for the stabilization of qubit
superpositions in regimes where standard theories predict an
effectively classical spin.},
Key = {fds365312}
}
@article{fds245047,
Author = {Zheng, H and Gauthier, DJ and Baranger, HU},
Title = {Decoy-state quantum key distribution with nonclassical light
generated in a one-dimensional waveguide.},
Journal = {Optics letters},
Volume = {38},
Number = {5},
Pages = {622-624},
Year = {2013},
Month = {March},
url = {http://www.ncbi.nlm.nih.gov/pubmed/23455244},
Abstract = {We investigate a decoy-state quantum key distribution (QKD)
scheme with a sub-Poissonian single-photon source, which is
generated on demand by scattering a coherent state off a
two-level system in a one-dimensional waveguide. We show
that, compared to coherent state decoy-state QKD, there is a
two-fold increase of the key generation rate. Furthermore,
the performance is shown to be robust against both parameter
variations and loss effects of the system.},
Doi = {10.1364/ol.38.000622},
Key = {fds245047}
}
@article{fds303604,
Author = {Zheng, H and Baranger, HU},
Title = {Persistent quantum beats and long-distance entanglement from
waveguide-mediated interactions.},
Journal = {Physical review letters},
Volume = {110},
Number = {11},
Pages = {113601},
Year = {2013},
Month = {March},
url = {http://arxiv.org/abs/1206.4442v2},
Abstract = {We study photon-photon correlations and entanglement
generation in a one-dimensional waveguide coupled to two
qubits with an arbitrary spatial separation. To treat the
combination of nonlinear elements and 1D continuum, we
develop a novel Green function method. The vacuum-mediated
qubit-qubit interactions cause quantum beats to appear in
the second-order correlation function. We go beyond the
Markovian regime and observe that such quantum beats persist
much longer than the qubit lifetime. A high degree of
long-distance entanglement can be generated, increasing the
potential of waveguide-QED systems for scalable quantum
networking.},
Doi = {10.1103/physrevlett.110.113601},
Key = {fds303604}
}
@article{fds221117,
Author = {H. Zheng and H. U. Baranger},
Title = {Persistent Quantum Beats and Long-Distance Entanglement from
Non-Markovian Processes},
Journal = {Phys. Rev. Lett.},
Volume = {110},
Pages = {113601},
Year = {2013},
Month = {March},
url = {http://www.phy.duke.edu/research/cm/bg/paper/ZhengB12_twoimp.pdf},
Doi = {10.1103/PhysRevLett.110.113601},
Key = {fds221117}
}
@article{fds303601,
Author = {Mehta, AC and Umrigar, CJ and Meyer, JS and Baranger,
HU},
Title = {Zigzag phase transition in quantum wires},
Journal = {Physical Review Letters},
Volume = {110},
Number = {24},
Pages = {246802},
Publisher = {American Physical Society (APS)},
Year = {2013},
Month = {June},
url = {http://arxiv.org/abs/1302.5429v2},
Abstract = {We study the quantum phase transition of interacting
electrons in quantum wires from a one-dimensional (1D)
linear configuration to a quasi-1D zigzag arrangement using
quantum Monte Carlo methods. As the density increases from
its lowest values, first, the electrons form a linear Wigner
crystal, then, the symmetry about the axis of the wire is
broken as the electrons order in a quasi-1D zigzag phase,
and, finally, the electrons form a disordered liquidlike
phase. We show that the linear to zigzag phase transition is
not destroyed by the strong quantum fluctuations present in
narrow wires; it has characteristics which are qualitatively
different from the classical transition. © 2013 American
Physical Society.},
Doi = {10.1103/PhysRevLett.110.246802},
Key = {fds303601}
}
@article{fds245046,
Author = {Liu, DE and Levchenko, A and Baranger, HU},
Title = {Floquet majorana fermions for topological qubits in
superconducting devices and cold-atom systems},
Journal = {Physical Review Letters},
Volume = {111},
Number = {4},
Pages = {047002},
Year = {2013},
Month = {July},
url = {http://www.ncbi.nlm.nih.gov/pubmed/23931396},
Abstract = {We develop an approach to realizing a topological phase
transition and non-Abelian braiding statistics with
dynamically induced Floquet Majorana fermions (FMFs). When
the periodic driving potential does not break fermion parity
conservation, FMFs can encode quantum information.
Quasienergy analysis shows that a stable FMF zero mode and
two other satellite modes exist in a wide parameter space
with large quasienergy gaps, which prevents transitions to
other Floquet states under adiabatic driving. We also show
that in the asymptotic limit FMFs preserve non-Abelian
braiding statistics and, thus, behave like their equilibrium
counterparts. © 2013 American Physical Society.},
Doi = {10.1103/PhysRevLett.111.047002},
Key = {fds245046}
}
@article{fds221156,
Author = {E. Novais and E. R. Mucciolo and H. U. Baranger},
Title = {Hamiltonian Methods in Quantum Error Correction and Fault
Tolerance},
Pages = {585-611},
Booktitle = {Quantum Error Correction},
Publisher = {Cambridge University Press},
Editor = {D. Lidar and P. Zanardi},
Year = {2013},
Month = {August},
url = {http://www.phy.duke.edu/research/cm/bg/paper/NovaisMB09_qecbook.pdf},
Key = {fds221156}
}
@article{fds221118,
Author = {H. Zheng and D. J. Gauthier and H. U. Baranger},
Title = {Waveguide-QED-Based Photonic Quantum Computation},
Journal = {Phys. Rev. Lett.},
Volume = {111},
Pages = {090502},
Year = {2013},
Month = {August},
url = {http://www.phy.duke.edu/research/cm/bg/paper/ZhengGB12_photongate.pdf},
Doi = {10.1103/PhysRevLett.111.090502},
Key = {fds221118}
}
@article{fds221154,
Author = {D. Ullmo and D. E. Liu and S. Burdin and H. U.
Baranger},
Title = {Fermi-liquid regime of the mesoscopic Kondo
problem},
Journal = {Eur. Phys. J. B},
Volume = {86},
Pages = {353},
Year = {2013},
Month = {August},
url = {http://www.phy.duke.edu/research/cm/bg/paper/UllmoLBB_fermiliqmesoKondo.pdf},
Doi = {10.1140/epjb/e2013-40418-3},
Key = {fds221154}
}
@article{fds303603,
Author = {Zheng, H and Gauthier, DJ and Baranger, HU},
Title = {Waveguide-QED-based photonic quantum computation.},
Journal = {Phys Rev Lett},
Volume = {111},
Number = {9},
Pages = {090502},
Publisher = {American Physical Society (APS)},
Year = {2013},
Month = {August},
url = {http://arxiv.org/abs/1211.1711v3},
Abstract = {We propose a new scheme for quantum computation using flying
qubits--propagating photons in a one-dimensional waveguide
interacting with matter qubits. Photon-photon interactions
are mediated by the coupling to a four-level system, based
on which photon-photon π-phase gates (CONTROLLED-NOT) can
be implemented for universal quantum computation. We show
that high gate fidelity is possible, given recent dramatic
experimental progress in superconducting circuits and
photonic-crystal waveguides. The proposed system can be an
important building block for future on-chip quantum
networks.},
Doi = {10.1103/PhysRevLett.111.090502},
Key = {fds303603}
}
@article{fds225583,
Author = {Y.-L. L. Fang and H. Zheng and H. U. Baranger},
Title = {One-Dimensional Waveguide Coupled to Multiple Qubits:
Photon-Photon Correlations},
Journal = {Eur. Phys. J. Quantum Technology},
Volume = {1},
Pages = {3},
Year = {2014},
Month = {January},
url = {http://arxiv.org/pdf/1308.6551v2.pdf},
Doi = {10.1140/epjqt3},
Key = {fds225583}
}
@article{fds303599,
Author = {Liu, DE and Zheng, H and Finkelstein, G and Baranger,
HU},
Title = {Tunable quantum phase transitions in a resonant level
coupled to two dissipative baths},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {89},
Number = {8},
Pages = {085116},
Publisher = {American Physical Society (APS)},
Year = {2014},
Month = {February},
url = {http://arxiv.org/abs/1310.4773v2},
Abstract = {We study tunneling through a resonant level connected to two
dissipative bosonic baths: one is the resistive environment
of the source and drain leads, while the second comes from
coupling to potential fluctuations on a resistive gate. We
show that several quantum phase transitions (QPT) occur in
such a model, transitions which emulate those found in
interacting systems such as Luttinger liquids or Kondo
systems. We first use bosonization to map this dissipative
resonant level model to a resonant level in a Luttinger
liquid, one with, curiously, two interaction parameters.
Drawing on methods for analyzing Luttinger liquids at both
weak and strong coupling, we obtain the phase diagram. For
strong dissipation, a Berezinsky-Kosterlitz-Thouless QPT
separates strong-coupling and weak-coupling (charge
localized) phases. In the source-drain symmetric case, all
relevant backscattering processes disappear at strong
coupling, leading to perfect transmission at zero
temperature. In fact, a QPT occurs as a function of the
coupling asymmetry or energy of the resonant level: the two
phases are (i) the system is cut into two disconnected
pieces (zero transmission), or (ii) the system is a single
connected piece with perfect transmission, except for a
disconnected fractional degree of freedom. The latter arises
from the competition between the two fermionic leads (source
and drain), as in the two-channel Kondo effect. © 2014
American Physical Society.},
Doi = {10.1103/PhysRevB.89.085116},
Key = {fds303599}
}
@article{fds225584,
Author = {D. E. Liu and H. Zheng and G. FInkelstein and H. U.
Baranger},
Title = {Tunable Quantum Phase Transitions in a Resonant Level
Coupled to Two Dissipative Baths},
Journal = {Phys. Rev. B},
Volume = {89},
Pages = {085116},
Year = {2014},
Month = {February},
url = {http://arxiv.org/pdf/1310.4773v2.pdf},
Doi = {10.1103/PhysRevB.89.085116},
Key = {fds225584}
}
@article{fds303600,
Author = {Bera, S and Florens, S and Baranger, HU and Roch, N and Nazir, A and Chin,
AW},
Title = {Stabilizing spin coherence through environmental
entanglement in strongly dissipative quantum
systems},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {89},
Number = {12},
Pages = {121108},
Publisher = {American Physical Society (APS)},
Year = {2014},
Month = {March},
url = {http://arxiv.org/abs/1307.5681v2},
Abstract = {The key feature of a quantum spin coupled to a harmonic bath
- a model dissipative quantum system - is competition
between oscillator potential energy and spin tunneling rate.
We show that these opposing tendencies cause environmental
entanglement through superpositions of adiabatic and
antiadiabatic oscillator states, which then stabilizes the
spin coherence against strong dissipation. This insight
motivates a fast-converging variational coherent-state
expansion for the many-body ground state of the spin-boson
model, which we substantiate via numerical quantum
tomography. © 2014 American Physical Society.},
Doi = {10.1103/PhysRevB.89.121108},
Key = {fds303600}
}
@article{fds225585,
Author = {S. Bera and S. Florens and H. U. Baranger and N. Roch and A. Nazir and A.
W. Chin},
Title = {Stabilizing Spin Coherence through Environmental
Entanglement in Strongly Dissipative Quantum
Systems},
Journal = {Phys. Rev. B},
Volume = {89},
Pages = {121108(R)},
Year = {2014},
Month = {March},
url = {http://arxiv.org/pdf/1307.5681v2.pdf},
Doi = {10.1103/PhysRevB.89.121108},
Key = {fds225585}
}
@article{fds245043,
Author = {Zheng, H and Florens, S and Baranger, HU},
Title = {Transport signatures of Majorana quantum criticality
realized by dissipative resonant tunneling},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {89},
Number = {23},
Pages = {235135},
Publisher = {American Physical Society (APS)},
Year = {2014},
Month = {June},
ISSN = {1098-0121},
url = {http://arxiv.org/pdf/1403.5175v1.pdf},
Abstract = {We consider theoretically the transport properties of a
spinless resonant electronic level coupled to strongly
dissipative leads, in the regime of circuit impedance near
the resistance quantum. Using the Luttinger liquid analogy,
one obtains an effective Hamiltonian expressed in terms of
interacting Majorana fermions, in which all environmental
degrees of freedom (leads and electromagnetic modes) are
encapsulated in a single fermionic bath. General transport
equations for this system are then derived in terms of the
Majorana T-matrix. A perturbative treatment of the Majorana
interaction term yields the appearance of a marginal, linear
dependence of the conductance on temperature when the system
is tuned to its quantum critical point, in agreement with
recent experimental observations. We investigate in detail
the different crossovers involved in the problem, and
analyze the role of the interaction terms in the transport
scaling functions. In particular, we show that single
barrier scaling applies when the system is slightly tuned
away from its Majorana critical point, strengthening the
general picture of dynamical Coulomb blockade. © 2014
American Physical Society.},
Doi = {10.1103/PhysRevB.89.235135},
Key = {fds245043}
}
@article{fds245042,
Author = {Bera, S and Nazir, A and Chin, AW and Baranger, HU and Florens,
S},
Title = {Generalized multipolaron expansion for the spin-boson model:
Environmental entanglement and the biased two-state
system},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {90},
Number = {7},
Pages = {075110},
Publisher = {American Physical Society (APS)},
Year = {2014},
Month = {August},
ISSN = {1098-0121},
url = {http://arxiv.org/pdf/1406.4983v2.pdf},
Abstract = {We develop a systematic variational coherent-state expansion
for the many-body ground state of the spin-boson model, in
which a quantum two-level system is coupled to a continuum
of harmonic oscillators. Energetic constraints at the heart
of this technique are rationalized in terms of polarons
(displacements of the bath states in agreement with
classical expectations) and antipolarons
(counterdisplacements due to quantum tunneling effects). We
present a comprehensive study of the ground-state two-level
system population and coherence as a function of tunneling
amplitude, dissipation strength, and bias (akin to asymmetry
of the double-well potential defining the two-state system).
The entanglement among the different environmental modes is
investigated by looking at spectroscopic signatures of the
bipartite entanglement entropy between a given environmental
mode and all the other modes. We observe a drastic change in
behavior of this entropy for increasing dissipation,
indicative of the entangled nature of the environmental
states. In addition, the entropy spreads over a large energy
range at strong dissipation, a testimony to the wide
entanglement window characterizing the underlying Kondo
state. Finally, comparisons to accurate numerical
renormalization-group calculations and to the exact Bethe
ansatz solution of the model demonstrate the rapid
convergence of our variationally optimized multipolaron
expansion, suggesting that it should also be a useful tool
for dissipative models of greater complexity, as relevant
for numerous systems of interest in quantum physics and
chemistry. © 2014 American Physical Society.},
Doi = {10.1103/PhysRevB.90.075110},
Key = {fds245042}
}
@article{fds330532,
Author = {Fang, YLL and Zheng, H and Baranger, HU},
Title = {One-dimensional waveguide coupled to multiple qubits:
Photon-photon correlations},
Journal = {EPJ Quantum Technology},
Volume = {1},
Number = {1},
Publisher = {Springer Science and Business Media LLC},
Year = {2014},
Month = {December},
url = {http://dx.doi.org/10.1140/epjqt3},
Abstract = {For a one-dimensional (1D) waveguide coupled to two or three
qubits, we show that the photon-photon correlations have a
wide variety of behavior, with structure that depends
sensitively on the frequency and on the qubit-qubit
separation L. We study the correlations by calculating the
second-order correlation function g 2 (t) in which the
interference among the photons multiply scattered from the
qubits causes rich structure. In one case, for example,
transmitted and reflected photons are both bunched
initially, but then become strongly anti-bunched for a long
time interval. We first calculate the correlation function
g2(t) including non-Markovian effects and then show that a
much simpler Markovian treatment, which can be solved
analytically, is accurate for small qubit separation. As a
result, the non-classical properties of microwaves in a 1D
waveguide coupled to many superconducting qubits with
experimentally accessible separation L could be readily
explored with our approach.},
Doi = {10.1140/epjqt3},
Key = {fds330532}
}
@article{fds245041,
Author = {Fang, YLL and Baranger, HU},
Title = {Waveguide QED: Power spectra and correlations of two photons
scattered off multiple distant qubits and a
mirror},
Journal = {Physical Review A - Atomic, Molecular, and Optical
Physics},
Volume = {91},
Number = {5},
Year = {2015},
Month = {May},
ISSN = {1050-2947},
url = {http://dx.doi.org/10.1103/PhysRevA.91.053845},
Abstract = {We study two-level systems (2LS) coupled at different points
to a one-dimensional waveguide in which one end is open and
the other is either open (infinite waveguide) or closed by a
mirror (semi-infinite). Upon injection of two photons
(corresponding to weak coherent driving), the resonance
fluorescence and photon correlations are shaped by the
effective qubit transition frequencies and decay rates,
which are substantially modified by interference effects. In
contrast to the well-known result in an infinite waveguide,
photons reflected by a single 2LS coupled to a semi-infinite
waveguide are initially bunched, a result that can be simply
explained by stimulated emission. As the number of 2LS
increases (up to 10 are considered here), rapid oscillations
build up in the correlations that persist for a very long
time. For instance, when the incoming photons are slightly
detuned, the transmitted photons in the infinite waveguide
are highly antibunched. On the other hand, upon resonant
driving, incoherently reflected photons are mostly
distributed within the photonic band gap and several sharp
side peaks. These features can be explained by considering
the poles of the single-particle Green function in the
Markovian regime combined with the time delay. Our
calculation is not restricted to the Markovian regime, and
we obtain several fully non-Markovian results. We show that
a single 2LS in a semi-infinite waveguide can not be
decoupled by placing it at the node of the photonic field,
in contrast to recent results in the Markovian regime. Our
results illustrate the complexities that ensue when several
qubits are strongly coupled to a bus (the waveguide) as
might happen in quantum information processing.},
Doi = {10.1103/PhysRevA.91.053845},
Key = {fds245041}
}
@article{fds318398,
Author = {Jin, LJ and Houzet, M and Meyer, JS and Baranger, HU and Hekking,
FWJ},
Title = {Detecting photon-photon interactions in a superconducting
circuit},
Journal = {Physical Review B - Condensed Matter and Materials
Physics},
Volume = {92},
Number = {13},
Publisher = {American Physical Society (APS)},
Year = {2015},
Month = {October},
url = {http://dx.doi.org/10.1103/PhysRevB.92.134503},
Abstract = {A local interaction between photons can be engineered by
coupling a nonlinear system to a transmission line. The
required transmission line can be conveniently formed from a
chain of Josephson junctions. The nonlinearity is generated
by side-coupling this chain to a Cooper pair box. We propose
to probe the resulting photon-photon interactions via their
effect on the current-voltage characteristic of a
voltage-biased Josephson junction connected to the
transmission line. Considering the Cooper pair box to be in
the weakly anharmonic regime, we find that the dc current
through the probe junction yields features around the
voltages 2eV=n ωs, where ωs is the plasma frequency of the
superconducting circuit. The features at n≥2 are a direct
signature of the photon-photon interaction in the
system.},
Doi = {10.1103/PhysRevB.92.134503},
Key = {fds318398}
}
@article{fds318397,
Author = {Bera, S and Baranger, HU and Florens, S},
Title = {Dynamics of a qubit in a high-impedance transmission line
from a bath perspective},
Journal = {Physical Review A},
Volume = {93},
Number = {3},
Publisher = {American Physical Society (APS)},
Year = {2016},
Month = {March},
url = {http://dx.doi.org/10.1103/PhysRevA.93.033847},
Abstract = {We investigate the quantum dynamics of a generic model of
light-matter interaction in the context of high-impedance
waveguides, focusing on the behavior of the photonic states
generated in the waveguide. The model treated consists
simply of a two-level system coupled to a bosonic bath (the
Ohmic spin-boson model). Quantum quenches as well as
scattering of an incident coherent pulse are studied using
two complementary methods. First, we develop an approximate
ansatz for the electromagnetic waves based on a single
multimode coherent state wave function; formally, this
approach combines in a single framework ideas from adiabatic
renormalization, the Born-Markov approximation, and
input-output theory. Second, we present numerically exact
results for scattering of a weak intensity pulse by using
numerical renormalization group (NRG) calculations. NRG
provides a benchmark for any linear response property
throughout the ultrastrong-coupling regime. We find that in
a sudden quantum quench, the coherent state approach
produces physical artifacts, such as improper relaxation to
the steady state. These previously unnoticed problems are
related to the simplified form of the ansatz that generates
spurious correlations within the bath. In the scattering
problem, NRG is used to find the transmission and reflection
of a single photon, as well as the inelastic scattering of
that single photon. Simple analytical formulas are
established and tested against the NRG data that predict
quantitatively the transport coefficients for up to moderate
environmental impedance. These formulas resolve pending
issues regarding the presence of inelastic losses in the
spin-boson model near absorption resonances, and could be
used for comparison to experiments in Josephson waveguide
quantum electrodynamics. Finally, the scattering results
using the coherent state wave-function approach are compared
favorably to the NRG results for very weak incident
intensity. We end our study by presenting results at higher
power where the response of the system is
nonlinear.},
Doi = {10.1103/PhysRevA.93.033847},
Key = {fds318397}
}
@article{fds318395,
Author = {Fang, Y-LL and Baranger, HU},
Title = {Photon correlations generated by inelastic scattering in a
one-dimensional waveguide coupled to three-level
systems},
Journal = {PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES},
Volume = {78},
Pages = {92-99},
Publisher = {ELSEVIER SCIENCE BV},
Year = {2016},
Month = {April},
url = {http://dx.doi.org/10.1016/j.physe.2015.11.004},
Abstract = {We study photon correlations generated by scattering from
three-level systems (3LS) in one dimension. The two systems
studied are a 3LS in a semi-infinite waveguide (3LS plus a
mirror) and two 3LS in an infinite waveguide (double 3LS).
Our two-photon scattering approach naturally connects photon
correlation effects with inelastically scattered photons; it
corresponds to input–output theory in the weak-probe
limit. At the resonance where electromagnetically induced
transparency (EIT) occurs, we find that no photons are
scattered inelastically and hence there are no induced
correlations. Slightly away from EIT, the total
inelastically scattered flux is large, being substantially
enhanced due to the additional interference paths. This
enhancement carries over to the two-photon correlation
function, which exhibits non-classical behavior such as
strong bunching with a very long time-scale. The long time
scale originates from the slow-light effect associated with
EIT.},
Doi = {10.1016/j.physe.2015.11.004},
Key = {fds318395}
}
@article{fds323837,
Author = {Zhang, G and Novais, E and Baranger, HU},
Title = {Rescuing a Quantum Phase Transition with Quantum
Noise.},
Journal = {Phys Rev Lett},
Volume = {118},
Number = {5},
Pages = {050402},
Publisher = {AMER PHYSICAL SOC},
Year = {2017},
Month = {February},
url = {http://dx.doi.org/10.1103/PhysRevLett.118.050402},
Abstract = {We show that placing a quantum system in contact with an
environment can enhance non-Fermi-liquid correlations,
rather than destroy quantum effects, as is typical. The
system consists of two quantum dots in series with two
leads; the highly resistive leads couple charge flow through
the dots to the electromagnetic environment, the source of
quantum noise. While the charge transport inhibits a quantum
phase transition, the quantum noise reduces charge transport
and restores the transition. We find a non-Fermi-liquid
intermediate fixed point for all strengths of the noise. For
strong noise, it is similar to the intermediate fixed point
of the two-impurity Kondo model.},
Doi = {10.1103/PhysRevLett.118.050402},
Key = {fds323837}
}
@article{fds328611,
Author = {Fang, YLL and Baranger, HU},
Title = {Multiple emitters in a waveguide: Nonreciprocity and
correlated photons at perfect elastic transmission},
Journal = {Physical Review A},
Volume = {96},
Number = {1},
Year = {2017},
Month = {July},
url = {http://dx.doi.org/10.1103/PhysRevA.96.013842},
Abstract = {We investigate interference and correlation effects when
several detuned emitters are placed along a one-dimensional
photonic waveguide. Such a setup allows multiple
interactions between the photons and the strongly coupled
emitters, and underlies proposed devices for quantum
information processing. We show, first, that a pair of
detuned two-level systems (2LS) separated by a half
wavelength mimic a driven Λ-type three-level system (3LS)
in both the single- and two-photon sectors. There is an
interference-induced transparency peak at which the
fluorescence is quenched, leaving the transmitted photons
completely uncorrelated. Slightly away from this separation,
we find that the inelastic scattering (fluorescence) is
large, leading to nonlinear effects such as nonreciprocity
(rectification). We connect this nonreciprocity to inelastic
scattering caused by driving a dark pole and so derive a
condition for maximum rectification. Finally, by placing a
true 3LS midway between the two 2LS, we show that elastic
scattering produces only transmission, but inelastic
scattering nevertheless occurs (the fluorescence is not
quenched) causing substantial photon correlations.},
Doi = {10.1103/PhysRevA.96.013842},
Key = {fds328611}
}
@article{fds330528,
Author = {Fang, Y-LL and Baranger, HU},
Title = {Waveguide QED: Power spectra and correlations of two photons
scattered off multiple distant qubits and a mirror (vol 91,
053845, 2015)},
Journal = {PHYSICAL REVIEW A},
Volume = {96},
Number = {5},
Pages = {1 pages},
Publisher = {AMER PHYSICAL SOC},
Year = {2017},
Month = {November},
url = {http://dx.doi.org/10.1103/PhysRevA.96.059904},
Doi = {10.1103/PhysRevA.96.059904},
Key = {fds330528}
}
@article{fds330529,
Author = {Zhang, XHH and Baranger, HU},
Title = {Quantum interference and complex photon statistics in
waveguide QED},
Journal = {Physical Review A},
Volume = {97},
Number = {2},
Pages = {023813-023813},
Publisher = {American Physical Society},
Year = {2018},
Month = {February},
url = {http://dx.doi.org/10.1103/PhysRevA.97.023813},
Abstract = {We obtain photon statistics by using a quantum jump approach
tailored to a system in which one or two qubits are coupled
to a one-dimensional waveguide. Photons confined in the
waveguide have strong interference effects, which are shown
to play a vital role in quantum jumps and photon statistics.
For a single qubit, for instance, the bunching of
transmitted photons is heralded by a jump that increases the
qubit population. We show that the distribution and
correlations of waiting times offer a clearer and more
precise characterization of photon bunching and
antibunching. Further, the waiting times can be used to
characterize complex correlations of photons which are
hidden in g(2)(τ), such as a mixture of bunching and
antibunching.},
Doi = {10.1103/PhysRevA.97.023813},
Key = {fds330529}
}
@article{fds330530,
Author = {Fang, Y-LL and Ciccarello, F and Baranger, HU},
Title = {Non-Markovian Dynamics of a Qubit Due to Single-Photon
Scattering in a Waveguide},
Journal = {New Journal of Physics},
Volume = {20},
Number = {4},
Pages = {043035-043035},
Publisher = {Institute of Physics (IoP) and Deutsche Physikalische
Gesellschaft},
Year = {2018},
Month = {April},
url = {http://dx.doi.org/10.1088/1367-2630/aaba5d},
Abstract = {We investigate the open dynamics of a qubit due to
scattering of a single photon in an infinite or
semi-infinite waveguide. Through an exact solution of the
time-dependent multi-photon scattering problem, we find the
qubitʼs dynamical map. Tools of open quantum systems theory
allow us then to show the general features of this map, find
the corresponding non-Linbladian master equation, and assess
in a rigorous way its non-Markovian nature. The qubit
dynamics has distinctive features that, in particular, do
not occur in emission processes. Two fundamental sources of
non-Markovianity are present: the finite width of the photon
wavepacket and the time delay for propagation between the
qubit and the end of the semi-infinite waveguide.},
Doi = {10.1088/1367-2630/aaba5d},
Key = {fds330530}
}
@article{fds339240,
Author = {Gheeraert, N and Zhang, XHH and Sépulcre, T and Bera, S and Roch, N and Baranger, HU and Florens, S},
Title = {Particle Production in Ultrastrong-Coupling Waveguide
QED},
Journal = {Physical Review A},
Volume = {98},
Number = {4},
Pages = {043816-043816},
Publisher = {American Physical Society (APS)},
Year = {2018},
Month = {October},
url = {http://dx.doi.org/10.1103/physreva.98.043816},
Abstract = {Understanding large-scale interacting quantum matter
requires dealing with the huge number of quanta that are
produced by scattering even a few particles against a
complex quantum object. Prominent examples are found from
high-energy cosmic ray showers, to the optical or electrical
driving of degenerate Fermi gases. We tackle this challenge
in the context of many-body quantum optics, as motivated by
the recent developments of circuit quantum electrodynamics
at ultrastrong coupling. The issue of particle production is
addressed quantitatively with a simple yet powerful concept
rooted in the quantum superposition principle of multimode
coherent states. This key idea is illustrated by the study
of multiphoton emission from a single two-level artificial
atom coupled to a high impedance waveguide, driven by a
nearly monochromatic coherent tone. We find surprisingly
that the off-resonant inelastic emission line shape is
dominated by broadband particle production, due to the large
phase space associated with contributions that do not
conserve the number of excitations. Such frequency
conversion processes produce striking signatures in time
correlation measurements, which can be tested experimentally
in quantum waveguides. These ideas open new directions for
the simulation of a variety of physical systems, from
polaron dynamics in solids to complex superconducting
quantum architectures.},
Doi = {10.1103/physreva.98.043816},
Key = {fds339240}
}
@article{fds341953,
Author = {Calajó, G and Fang, Y-LL and Baranger, HU and Ciccarello,
F},
Title = {Exciting a Bound State in the Continuum through Multiphoton
Scattering Plus Delayed Quantum Feedback.},
Journal = {Phys Rev Lett},
Volume = {122},
Number = {7},
Pages = {073601},
Publisher = {American Physical Society (APS)},
Year = {2019},
Month = {February},
url = {http://dx.doi.org/10.1103/PhysRevLett.122.073601},
Abstract = {Excitation of a bound state in the continuum (BIC) through
scattering is problematic since it is by definition
uncoupled. Here, we consider a type of dressed BIC and show
that it can be excited in a nonlinear system through
multiphoton scattering and delayed quantum feedback. The
system is a semi-infinite waveguide with linear dispersion
coupled to a qubit, in which a single-photon, dressed BIC is
known to exist. We show that this BIC can be populated via
multiphoton scattering in the non-Markovian regime, where
the photon delay time (due to the qubit-mirror distance) is
comparable with the qubit's decay. A similar process excites
the BIC existing in an infinite waveguide coupled to two
distant qubits, thus yielding stationary entanglement
between the qubits. This shows, in particular, that
single-photon trapping via multiphoton scattering can occur
without band edge effects or cavities, the essential
resource being instead the delayed quantum feedback provided
by a single mirror or the emitters themselves.},
Doi = {10.1103/PhysRevLett.122.073601},
Key = {fds341953}
}
@article{fds342551,
Author = {Zhang, XHH and Baranger, HU},
Title = {Heralded Bell State of Dissipative Qubits Using Classical
Light in a Waveguide.},
Journal = {Physical Review Letters},
Volume = {122},
Number = {14},
Pages = {140502-140502},
Year = {2019},
Month = {April},
url = {http://dx.doi.org/10.1103/PhysRevLett.122.140502},
Abstract = {Maximally entangled two-qubit states (Bell states) are of
central importance in quantum technologies. We show that
heralded generation of a maximally entangled state of two
intrinsically open qubits can be realized in a
one-dimensional (1D) system through strong coherent driving
and continuous monitoring. In contrast to the natural idea
that dissipation leads to decoherence and so destroys
quantum effects, continuous measurement and strong
interference in our 1D system generate a pure state with
perfect quantum correlation between the two open qubits.
Though the steady state is a trivial product state that has
zero coherence or concurrence, we show that, with carefully
tuned parameters, a Bell state can be generated in the
system's quantum jump trajectories, heralded by a reflected
photon. Surprisingly, this maximally entangled state
survives the strong coherent state input-a classical state
that overwhelms the system. This simple method to generate
maximally entangled states using classical coherent light
and photon detection may, since our qubits are in a 1D
continuum, find application as a building block of quantum
networks.},
Doi = {10.1103/PhysRevLett.122.140502},
Key = {fds342551}
}
@article{fds347974,
Author = {Zhao, L and Arnault, EG and Bondarev, A and Seredinski, A and Larson, T and Draelos, AW and Li, H and Watanabe, K and Taniguchi, T and Amet, F and Baranger, HU and Finkelstein, G},
Title = {Interference of Chiral Andreev Edge States},
Journal = {Nature Physics},
Volume = {16},
Number = {8},
Pages = {862-867},
Publisher = {Springer Nature},
Year = {2020},
Month = {May},
url = {http://dx.doi.org/10.1038/s41567-020-0898-5},
Abstract = {The search for topological excitations such as Majorana
fermions has spurred interest in the boundaries between
distinct quan- tum states. Here, we explore an interface
between two prototypical phases of electrons with
conceptually different ground states: the integer quantum
Hall insulator and the s-wave superconductor. We find clear
signatures of hybridized electron and hole states similar to
chiral Majorana fermions, which we refer to as chiral
Andreev edge states (CAESs). These propagate along the
interface in the direction determined by the magnetic field
and their interference can turn an incoming electron into an
out- going electron or hole, depending on the phase
accumulated by the CAESs along their path. Our results
demonstrate that these excitations can propagate and
interfere over a significant length, opening future
possibilities for their coherent manipulation.},
Doi = {10.1038/s41567-020-0898-5},
Key = {fds347974}
}
@article{fds347976,
Author = {Zhang, G and Baranger, HU},
Title = {Stabilization of a Majorana Zero Mode through Quantum
Frustration.},
Journal = {Physical Review B},
Volume = {102},
Pages = {035103-035103},
Year = {2020},
Month = {July},
url = {http://dx.doi.org/10.1103/PhysRevB.102.035103},
Abstract = {We analyze a system in which a topological Majorana zero
mode (MZM) combines with a MZM produced by quantum
frustration. At the boundary between the topological and
non-topological states, a MZM does not appear. The system
that we study combines two parts, a grounded topological
superconducting wire that hosts two MZM at its ends, and an
on-resonant quantum dot connected to two dissipative leads.
The quantum dot with dissipative leads creates an effective
two-channel Kondo (2CK) state in which quantum frustration
yields an isolated MZM at the dot. We find that coupling the
dot to one of the wire Majoranas stabilizes the MZM at the
other end of the wire. In addition to providing a route to
achieving an unpaired Majorana zero mode, this scheme
provides a clear signature of the presence of the 2CK
Majorana.},
Doi = {10.1103/PhysRevB.102.035103},
Key = {fds347976}
}
@article{fds330531,
Author = {Zhang, G and Chung, C-H and Ke, C-T and Lin, C-Y and Mebrahtu, H and Smirnov, AI and Finkelstein, G and Baranger, HU},
Title = {Nonequilibrium quantum critical steady state: Transport
through a dissipative resonant level},
Journal = {Physical Review Research},
Volume = {3},
Number = {1},
Pages = {013136-013136},
Publisher = {American Physical Society (APS)},
Year = {2021},
Month = {February},
url = {https://arxiv.org/abs/1609.04765},
Abstract = {Nonequilibrium properties of correlated quantum matter are
being intensively investigated because of the rich interplay
between external driving and the many-body correlations. Of
particular interest is the nonequilibrium behavior near a
quantum critical point (QCP), where the system is delicately
balanced between different ground states. We present both an
analytical calculation of the nonequilibrium steady-state
current in a critical system and experimental results to
which the theory is compared. The system is a quantum dot
coupled to resistive leads: a spinless resonant level
interacting with an ohmic dissipative environment. A
two-channel Kondo-like QCP occurs when the level is on
resonance and symmetrically coupled to the leads, conditions
achieved by fine tuning using electrostatic gates. We
calculate and measure the nonlinear current as a function of
bias (I−V curve) at the critical values of the gate
voltages corresponding to the QCP. The quantitative
agreement between the experimental data and the theory, with
no fitting parameter, is excellent. As our system is fully
accessible to both theory and experiment, it provides an
ideal setting for addressing nonequilibrium phenomena in
correlated quantum matter.},
Doi = {10.1103/physrevresearch.3.013136},
Key = {fds330531}
}
@article{fds354093,
Author = {Zhang, XHH and Baranger, HU},
Title = {Driven-Dissipative Phase Transition in a Kerr Oscillator:
From Semi-Classical PT Symmetry to Quantum
Fluctuations.},
Journal = {Physical Review A},
Volume = {103},
Pages = {033711-033711},
Publisher = {American Physical Society},
Year = {2021},
Month = {March},
url = {https://arxiv.org/abs/2007.01422},
Abstract = {We study a minimal model that has a driven-dissipative
quantum phase transition, namely a Kerr non-linear
oscillator subject to driving and dissipation. Using
mean-field theory, exact diagonalization, and the Keldysh
formalism, we analyze the critical phenomena in this system,
showing which aspects can be captured by each approach and
how the approaches complement each other. Then critical
scaling and finite-size scaling are calculated analytically
using the quantum Langevin equation. The physics contained
in this simple model is surprisingly rich: it includes a
continuous phase transition, Z2 symmetry breaking, PT
symmetry, state squeezing, and critical fluctuations. Due to
its simplicity and solvability, this model can serve as a
paradigm for exploration of open quantum many-body
physics.},
Doi = {10.1103/PhysRevA.103.033711},
Key = {fds354093}
}
@article{fds359884,
Author = {Zhang, G and Novais, E and Baranger, HU},
Title = {Conductance of a dissipative quantum dot: Nonequilibrium
crossover near a non-Fermi-liquid quantum critical
point},
Journal = {Physical Review B},
Volume = {104},
Pages = {165423-165423},
Publisher = {American Physical Society (APS)},
Year = {2021},
Month = {October},
url = {https://arxiv.org/abs/2108.00064},
Abstract = {We find the nonlinear conductance of a dissipative resonant
level in the nonequilibrium steady state near its quantum
critical point. The system consists of a spin-polarized
quantum dot connected to two resistive leads that provide
ohmic dissipation. We focus on the crossover from the
strong-coupling, non-Fermi-liquid regime to the
weak-coupling, Fermi-liquid ground state, a crossover driven
by the instability of the quantum critical point to
hybridization asymmetry or detuning of the level in the dot.
We show that the crossover properties are given by tunneling
through an effective single barrier described by the
boundary sine-Gordon model. The nonlinear conductance is
then obtained from thermodynamic Bethe ansatz results in the
literature, which were developed to treat tunneling in a
Luttinger liquid. The current-voltage characteristics are
thus found for any value of the resistance of the leads. For
the special case of lead resistance equal to the quantum
resistance, we find mappings onto, first, the two-channel
Kondo model and, second, an effectively noninteracting model
from which the nonlinear conductance is found analytically.
A key feature of the general crossover function is that the
nonequilibrium crossover driven by applied bias is different
from the crossover driven by temperature—we find that the
nonequilibrium crossover is substantially sharper. Finally,
we compare to experimental results for both the bias and
temperature crossovers: the agreement is
excellent.},
Doi = {10.1103/physrevb.104.165423},
Key = {fds359884}
}
@article{fds369063,
Author = {Lee, JW and Baranger, HU},
Title = {Quantum critical region of a two-dimensional spin-half XXZ
model},
Journal = {Journal of the Korean Physical Society},
Volume = {82},
Number = {7},
Pages = {688-691},
Year = {2023},
Month = {April},
url = {http://dx.doi.org/10.1007/s40042-023-00725-w},
Abstract = {We study the properties of a quantum critical region of an
XXZ model in two dimensions. The quantum critical point at
zero temperature evolves as the temperature increases. Using
the quantum Monte Carlo method with stochastic series
expansions, we simulated the lattices of which size are up
to 200 × 200. For the finite-temperature transitions from a
paramagnet to an XY critical phase, we measured the
superfluid stiffness and used the finite-size scaling to
obtain the critical temperatures. For the
paramagnet-to-antiferromagnetic transitions, we measured the
compressibility to obtain the critical points. With these
critical points, we constructed the finite-temperature phase
diagram of the XXZ model in two dimensions.},
Doi = {10.1007/s40042-023-00725-w},
Key = {fds369063}
}
%% Papers Submitted
@article{Lee06_disordsuper,
Author = {J.-W. Lee and S. Chandrasekharan and H. U.
Baranger},
Title = {Disorder Induced Superconductivity of Hard-Core Bosons in
Two Dimensions},
Journal = {submitted to Phys. Rev. B},
Year = {2007},
Key = {Lee06_disordsuper}
}