Theory of relaxation oscillations in exciton-polariton condensates

TL;DR

This paper analyzes relaxation oscillations in exciton-polariton condensates using analytical and numerical methods, revealing conditions for oscillation occurrence and the importance of a second reservoir in pulsed excitation.

Contribution

It provides a new analytical condition for relaxation oscillations and explores the dynamics of polariton condensates with a coupled reservoir model.

Findings

Relaxation oscillations occur in systems with short polariton lifetime.

A second reservoir is necessary for oscillations under pulsed excitation.

Phase space analysis classifies different condensate dynamic regimes.

Abstract

We provide an analytical and numerical description of relaxation oscillations in the nonresonantly pumped polariton condensate. The presented considerations are based on the open dissipative Gross-Pitaevskii equation coupled to a pair of rate equations. The evolution of the condensate density can be explained qualitatively by studying the topology of the trajectory in phase space. We use a fixed points analysis for the classification of the different regimes of condensate dynamics, including fast stabilization, slow oscillations and ultrashort pulse emission. We obtain an analytical condition for the occurrence of relaxation oscillations. Continuous and pulsed condensate excitation considered and we demonstrate that in the latter case the existence of the second reservoir is necessary for the emergence of oscillations. We show that relaxation oscillations should be expected to occur in systems with relatively short polariton lifetime.