The negative Bogoliubov dispersion in exciton-polariton condensates

TL;DR

This paper theoretically investigates the conditions under which the negative Bogoliubov dispersion branch can be observed in exciton-polariton condensates through photoluminescence spectra, considering reservoir effects and relaxation oscillations.

Contribution

It provides a theoretical analysis of the negative Bogoliubov dispersion in exciton-polariton condensates, including the effects of reservoirs and relaxation oscillations on observability.

Findings

Negative dispersion becomes visible at high excitation densities.

Reservoir effects influence the photoluminescence spectra.

Relaxation oscillations can enhance the visibility of the negative branch.

Abstract

Bogoliubov's theory states that self-interaction effects in Bose-Einstein condensates produce a characteristic linear dispersion at low momenta. One of the curious features of Bogoliubov's theory is that the new quasiparticles in the system are linear combinations of creation and destruction operators of the bosons. In exciton-polariton condensates, this gives the possibility of directly observing the negative branch of the Bogoliubov dispersion in the photoluminescence (PL) emission. Here we theoretically examine the PL spectra of exciton-polariton condensates taking into account of reservoir effects. At sufficiently high excitation densities, the negative dispersion becomes visible. We also discuss the possibility for relaxation oscillations to occur under conditions of strong reservoir coupling. This is found to give a secondary mechanism for making the negative branch visible.