Thermal decoherence of a nonequilibrium polariton fluid

TL;DR

This study investigates how thermal effects influence the coherence and phase structure of a nonequilibrium polariton condensate in microcavities, revealing significant coherence loss with increased heating.

Contribution

It demonstrates controlled heating of a polariton condensate and directly measures heat absorption effects on spatial coherence and phase structures, linking experimental results with stochastic mean field theory.

Findings

Coherence length decreases with increased heating.

Localized phase structures disappear as temperature rises.

Heat pickup significantly impacts the order parameter in nonequilibrium quantum fluids.

Abstract

Exciton-polaritons constitute a unique realization of a quantum fluid interacting with its environment. Using Selenide based microcavities, we exploit this feature to warm up a polariton condensate in a controlled way and monitor its spatial coherence. We determine directly the amount of heat picked up by the condensate by measuring the phonon-polariton scattering rate and comparing it with the loss rate. We find that upon increasing the heating rate, the spatial coherence length decreases markedly, while localized phase structures vanish, in good agreement with a stochastic mean field theory. From the thermodynamical point-of-view, this regime is unique as it involves a nonequilibrium quantum fluid with no well-defined temperature, but which is nevertheless able to pick up heat with dramatic effects on the order parameter.