Non-equilibrium properties of a pumped-decaying Bose-condensed electron-hole gas in the BCS-BEC crossover region

TL;DR

This paper models a non-equilibrium exciton Bose-condensed gas, revealing how continuous electron-hole supply suppresses BEC through quasi-particle excitations, affecting the system's stability and phase transition.

Contribution

It introduces a theoretical framework combining BCS-Leggett theory with Keldysh formalism to analyze non-equilibrium effects on exciton BEC.

Findings

BEC is suppressed in non-equilibrium steady states

Electron-hole supply induces quasi-particle excitations

Steady state stability is affected by quasi-particle occupation

Abstract

We theoretically investigate a Bose-condensed exciton gas out of equilibrium. Within the framework of the combined BCS-Leggett strong-coupling theory with the non-equilibrium Keldysh formalism, we show how the Bose-Einstein condensation (BEC) of excitons is suppressed to eventually disappear, when the system is in the non-equilibrium steady state. The supply of electrons and holes from the bath is shown to induce quasi-particle excitations, leading to the partial occupation of the upper branch of Bogoliubov single-particle excitation spectrum. We also discuss how this quasi-particle induction is related to the suppression of exciton BEC, as well as the stability of the steady state.