Spontaneous microcavity-polariton coherence across the parametric threshold: Quantum Monte Carlo studies

TL;DR

This study uses Quantum Monte Carlo simulations to analyze how spontaneous coherence emerges in microcavity polaritons at the parametric threshold, revealing a phase transition from incoherent to coherent emission.

Contribution

It introduces a non-equilibrium phase transition framework for microcavity polariton coherence using Quantum Monte Carlo methods, highlighting differences between 2D and quasi-1D systems.

Findings

Coherence length diverges at the threshold in 2D microcavities.

Above threshold, emission becomes phase-coherent across the sample.

In quasi-1D systems, coherence remains finite even above the threshold.

Abstract

We investigate the appearance of spontaneous coherence in the parametric emission from planar semiconductor microcavities in the strong coupling regime. Calculations are performed by means of a Quantum Monte Carlo technique based on the Wigner representation of the coupled exciton and cavity-photon fields. The numerical results are interpreted in terms of a non-equilibrium phase transition occurring at the parametric oscillation threshold: below the threshold, the signal emission is incoherent, and both the first and the second-order coherence functions have a finite correlation length which becomes macroscopic as the threshold is approached. Above the threshold, the emission is instead phase-coherent over the whole two-dimensional sample and intensity fluctuations are suppressed. Similar calculations for quasi-one-dimensional microcavities show that in this case the phase-coherence of the signal emission has a finite extension even above the threshold, while intensity fluctuations are suppressed.