Nonequilibrium polariton dynamics in a Bose-Einstein condensate coupled to an optical cavity

TL;DR

This paper investigates the nonequilibrium dynamics of a Bose-Einstein condensate coupled to an optical cavity, revealing structured fluctuation spectra, resonant damping effects, and the separation of dissipation mechanisms using advanced Green's function techniques.

Contribution

It provides a detailed analysis of polariton-like excitations and fluctuation spectra, highlighting the effects of Beliaev damping and photon loss in cavity-coupled condensates.

Findings

Resonant enhancement of Beliaev damping confirmed

Structured fluctuation spectrum with spectral hole burning observed

Beliaev process does not affect self-organization criticality

Abstract

We study quasiparticle scattering effects on the dynamics of a homogeneous Bose-Einstein condensate of ultracold atoms coupled to a single mode of an optical cavity. The relevant excitations, which are polariton-like mixed excitations of photonic and atomic density-wave modes, are identified. All the first-order correlation functions are presented by means of the Keldysh Green's function technique. Beyond confirming the existence of the resonant enhancement of Beliaev damping, we find a very structured spectrum of fluctuations. There is a spectral hole burning at half of the recoil frequency reflecting the singularity of the Beliaev scattering process. The effects of the photon-loss dissipation channel and that of the Beliaev damping due to atom-atom collisions can be well separated. We show that the Beliaev process does not influence the properties of the self-organization criticality.