Speaker
Description
Recently, the existence of Dicke-like equilibrium superradiant phase transitions in cavity QED many-body system has been put into question — resulting in no-go theorems on spontaneous photon condensation. Specifically, the no-go theorems tells us that the superradiant phase transition is prohibited as long as a single-mode purely electrical vector potential is considered, with the transition being analogous to a magnetostatic instability. In this work [1] we consider a minimal setting beyond 1D – i.e., a two-leg ladder – where the orbital motion of spinless fermions is coupled through Peierls substitution to a non-uniform cavity mode which generates a fluctuating magnetic field. Thanks to the quasi-one dimensional geometry we are able to scrutinize the accuracy of (mean field) cavity-matter decoupling against large scale density-matrix renormalization group simulations and study light-matter entanglement properties as well as the exact cavity state. Our results show that ladder geometries can indeed photon condensation and in particular they serve as a first simple example of first-order photon condensation in a gauge-invariant scenario; highlighting how, in the quest for photon condensed phases, looking for only second order instabilities might be limiting.
[1] arXiv:2302.09901v2
| Abstract category | Quantum Optics |
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