Thermo-optical interactions in a dye-microcavity photon Bose-Einstein condensate

TL;DR

This paper theoretically explores how thermo-optic effects influence photon Bose-Einstein condensates in dye microcavities, suggesting conditions under which superfluidity might emerge despite the unique thermalization process.

Contribution

It introduces a theoretical framework for thermo-optic photon interactions and predicts a superfluid-like excitation spectrum in dye microcavity photon condensates.

Findings

Thermo-optic effects induce effective photon interactions.

Predicted linear dispersion at low momenta satisfies superfluidity criteria.

Long-range, delayed interactions could lead to novel quantum fluid phenomena.

Abstract

Superfluidity and Bose-Einstein condensation are usually considered as two closely related phenomena. Indeed, in most macroscopic quantum systems, like liquid helium, ultracold atomic Bose gases, and exciton-polaritons, condensation and superfluidity occur in parallel. In photon Bose-Einstein condensates realized in the dye microcavity system, thermalization does not occur by direct interaction of the condensate particles as in the above described systems, i.e. photon-photon interactions, but by absorption and re-emission processes on the dye molecules, which act as a heat reservoir. Currently, there is no experimental evidence for superfluidity in the dye microcavity system, though effective photon interactions have been observed from thermo-optic effects in the dye medium. In this work, we theoretically investigate the implications of effective thermo-optic photon interactions, a temporally delayed and spatially non-local effect, on the photon condensate, and derive the resulting Bogoliubov excitation spectrum. The calculations suggest a linear photon dispersion at low momenta, fulfilling the Landau's criterion of superfluidity . We envision that the temporally delayed and long-range nature of the thermo-optic photon interaction offer perspectives for novel quantum fluid phenomena.