Photoluminescence and gain/absorption spectra of a driven-dissipative electron-hole-photon condensate

TL;DR

This paper provides a theoretical analysis of nonequilibrium effects on photoluminescence and gain/absorption spectra of driven-dissipative exciton-polariton condensates, revealing suppression of certain spectral features and the presence of ghost branches.

Contribution

It extends the Hartree-Fock-Bogoliubov theory with the Keldysh formalism to analyze nonequilibrium spectral properties of exciton-polariton condensates, aligning theory with experimental observations.

Findings

Photoluminescence spectra show a blue shift and diffusive Goldstone mode.

Nonequilibrium effects suppress the visibility of the Bogoliubov dispersion in the spectra.

Ghost branches are detectable as hole burning effects in gain/absorption spectra.

Abstract

We investigate theoretically nonequilibrium effects on photoluminescence and gain/absorption spectra of a driven-dissipative exciton-polariton condensate, by employing the combined Hartree-Fock-Bogoliubov theory with the generalized random phase approximation extended to the Keldysh formalism. Our calculated photoluminescence spectra is in semiquantitative agreement with experiments, where features such as a blue shift of the emission from the condensate, the appearance of the dispersionless feature of a diffusive Goldstone mode, and the suppression of the dispersive profile of the mode are obtained. We show that the nonequilibrium nature of the exciton-polariton condensate strongly suppresses the visibility of the Bogoliubov dispersion in the negative energy branch (ghost branch) in photoluminescence spectra. We also show that the trace of this branch can be captured as a hole burning effect in gain/absorption spectra. Our results indicate that the nonequilibrium nature of the exciton-polariton condensate strongly reduces quantum depletion, while a scattering channel to the ghost branch is still present.