Spontaneous symmetry breaking in a polariton and photon laser

TL;DR

This paper demonstrates spontaneous symmetry breaking and long-range spatial coherence in semiconductor microcavities during polariton and photon lasing, revealing stochastic polarization behavior and meeting criteria for Bose-Einstein condensation.

Contribution

It provides the first simultaneous observation of symmetry breaking and long-range order in both polariton and photon lasing regimes in a semiconductor microcavity.

Findings

Stochastic polarization buildup observed in both regimes

Spatial coherence develops alongside polarization

Landau and Penrose-Onsager criteria are satisfied

Abstract

We report on the simultaneous observation of spontaneous symmetry breaking and long-range spatial coherence both in the strong and the weak-coupling regime in a semiconductor microcavity. Under pulsed excitation, the formation of a stochastic order parameter is observed in polariton and photon lasing regimes. Single-shot measurements of the Stokes vector of the emission exhibit the buildup of stochastic polarization. Below threshold, the polarization noise does not exceed 10%, while above threshold we observe a total polarization of up to 50% after each excitation pulse, while the polarization averaged over the ensemble of pulses remains nearly zero. In both polariton and photon lasing regimes, the stochastic polarization buildup is accompanied by the buildup of spatial coherence. We find that the Landau criterion of spontaneous symmetry breaking and Penrose-Onsager criterion of long-range order for Bose-Einstein condensation are met in both polariton and photon lasing regimes.