The broad focus of Prof. Baranger's group is the interplay of electron-electron interactions and quantum interference at the nanoscale. Fundamental interest in nanophysics - the physics of small, nanometer scale, bits of solid - stems from the ability to control and probe systems on length scales larger than atoms but small enough that the averaging inherent in bulk properties has not yet occurred. Using this ability, entirely unanticipated phenomena can be uncovered on the one hand, and the microscopic basis of bulk phenomena can be probed on the other. Additional interest comes from the many links between nanophysics and nanotechnology. Within this thematic area, our work ranges from projects trying to nail down realistic behavior in well-characterized systems, to more speculative projects reaching beyond regimes investigated experimentally to date.
Correlations between particles are a central issue in many areas of condensed matter physics, from emergent many-body phenomena in complex materials, to strong matter-light interactions in quantum information contexts, to transport properties of single molecules. Such correlations, for either electrons or bosons, underlie key phenomena in nanostructures (Coulomb blockade, photon blockade, Luttinger liquid, and various tunable Kondo effects). Using the exquisite control of nanostructures now possible, experimentalists will be able to engineer correlations in nanosystems in the near future. Of particular interest are cases in which one can tune the competition between different types of correlation, or in which correlation can be tunably enhanced or suppressed by other effects (such as interference, confinement, or temperature), potentially causing a quantum phase transition-- a sudden, qualitative change in the correlations in the system.
My recent work has addressed correlations in both electronic systems (quantum wires and dots) and photonic systems (photon waveguides). We have focused on four different systems: (1) quantum dot in a dissipative environment, (2) photonic waveguide connected to qubits, (3) dynamics of a semiconductor wire on a superconductor, and (4) quantum phase transitions in low density electron gas in a quantum wire. The methods used are both analytical and numerical, and are closely linked to experiments.