Cooperative phase transitions in the system of photons and dye molecules

Bose condensed light can form new phases [1] in a dye filled cavity due to the presence of the orientational disorder in the ensemble of dye molecules which are essentially frozen on the time scale of the photonic thermalization (few ps). At longer time scales (few ns) molecular degrees of freedom -- orientations and positions -- become important. Here it is shown that including these degrees of freedom on equal footing with photons can change the nature of the photonic condensation -- it can proceed as Ist order phase transition which can also result in the mutual phase separation effect -- for photons and dye. The analysis is conducted within the mean field approach.