High temperature phase transition in the coupled atom-light system in   the presence of optical collisions
  The problem of photonic phase transition for the system of a two-level atomic ensemble interacting with a quantized single-mode electromagnetic field in the presence of optical collisions (OC) is considered. We have shown that for large and negative atom-field detuning a photonic field exhibits high temperature second order phase transition to superradiant state under thermalization condition for coupled atom-light states. Such a transition can be connected with superfluid (coherent) properties of photon-like low branch (LB) polaritons. We discuss the application of metallic cylindrical waveguide for observing predicted effects. 
A.P. Alodjants, I.Yu. Chestnov, S.M. Arakelian
cond-mat.mes-hall physics.atom-ph