Thermo-Optic Photon-Photon Interaction in Photon BECs at Dimensional Crossover from 2D to 1D

Since the discovery of photon Bose-Einstein condensates in 2010 [1] this phenomenon has been studied extensively. At its core this system consists of a dye solution filling the microcavity in which the photons are trapped. Due to cyclic absorption and reemission processes of photons the dye leads to a thermalisation of the photon gas at room temperature and finally to its Bose-Einstein condensation. Because of a non-ideal quantum efficiency, those cycles yield in addition a heating of the dye solution, which results in an effective photon-photon interaction [2].

This talk studies theoretically the dimensional crossover from a two- to a one-dimensional photon BEC. Whereas, recently the thermodynamic properties were discussed in the non-interacting case [3], we focus here at the strength of the thermo-optic photon-photon interaction. To this end we use at first an extended Gross-Pitaevskii model and investigate how to deduce the effective photon-photon interaction strength from the condensate profile. Afterwards, we analyze how the many-body energy states drift due to the presence of the thermo-optic interaction in a thermalised photon BEC. In both cases we compare the results for an anisotropic harmonic confinement with those for a non-symmetric box potential. 

[1] J. Klaers, J. Schmitt, F. Vewinger, and M. Weitz, Nature 468, 545 (2010) 

[2] E. Stein, F. Vewinger, and A. Pelster, New J. Phys. 21, 103044 (2019)

[3] E. Stein, and A. Pelster, arXiv:2011.06339