Publications [#382846] of Henry Everitt

Papers Published

1. Kim, D; Dasgupta, S; Ma, X; Park, J-M; Wei, H-T; Li, X; Luo, L; Doumani, J; Yang, W; Cheng, D; Kim, RHJ; Everitt, HO; Kimura, S; Nojiri, H; Wang, J; Cao, S; Bamba, M; Hazzard, KRA; Kono, J, Observation of the magnonic Dicke superradiant phase transition., Science advances, vol. 11 no. 14 (April, 2025), pp. eadt1691 [doi]
   (last updated on 2025/11/07)

   Abstract:
   Two-level atoms ultrastrongly coupled with single-mode cavity photons are predicted to exhibit a quantum phase transition, entering a phase in which both the atomic polarization and the photonic field are finite even without external driving. However, this phenomenon, the superradiant phase transition (SRPT), is forbidden by a no-go theorem due to the existence of the diamagnetic term. Here, we present spectroscopic evidence for a magnonic SRPT in ErFeO₃, where the role of the photonic mode (two-level atoms) in the photonic SRPT is played by an Fe³⁺ magnon mode (Er³⁺ spins). The absence of the diamagnetic term in the Fe³⁺-Er³⁺ exchange coupling ensures that the no-go theorem does not apply. Ultrabroadband terahertz and gigahertz magnetospectroscopy experiments revealed the signatures of the SRPT in thermal equilibrium, a kink and a softening, respectively, of two spin-magnon hybridized modes at the critical point. Systems near this phase are expected to harbor large-scale squeezing, which will potentially provide a route to next-generation quantum technologies.