Cooperative phase transitions in the system of photons and dye molecules

TL;DR

This paper investigates how including molecular degrees of freedom affects the phase transition of Bose condensed light in dye-filled cavities, revealing possible first-order transitions and phase separation.

Contribution

It introduces a mean field model accounting for molecular orientations and positions, showing their impact on the nature of photonic Bose condensation.

Findings

Molecular degrees of freedom can induce first-order phase transitions in photonic condensates.

The study predicts mutual phase separation between photons and dye molecules.

Experimental detection strategies for the transition are proposed.

Abstract

Bose condensed light can form new phases [1] in a dye filled cavity due to the presence of the orientational disorder created by dye molecules which are essentially frozen on the time scale of the photonic thermalization (few ps). At longer times (few ns) molecular degrees of freedom -- orientations and positions -- become important. Including them 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 in the thermodynamic limit. Recommendations for the experimental detection of the transition nature are formulated.