G. M. Andolina, F. M. D. Pellegrino, V. Giovannetti, A. H. MacDonald, M. Polini
Published 2019-05-27Version 1
In spite of decades of work it has remained unclear whether or not superradiant quantum phases, referred to here as photon condensates, can occur in equilibrium. In this Letter, we first show that when a non-relativistic quantum many-body system is coupled to a cavity field, gauge invariance forbids photon condensation. We then present a microscopic theory of the cavity quantum electrodynamics of an extended Falicov-Kimball model, showing that, in agreement with the general theorem, its insulating ferroelectric and exciton condensate phases are not altered by the cavity and do not support photon condensation.
Hydrodynamic description of transport in strongly correlated electron systems
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No-go theorem for photon condensation: a non-perturbative extension to first-order phase transitions
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