Signatures of a dissipative phase transition in photon correlation measurements

TL;DR

This paper demonstrates that photon correlation measurements can effectively characterize dissipative phase transitions in driven-dissipative systems, revealing critical slowing down and quantum fluctuation effects in optical bistability.

Contribution

It introduces a method to detect dissipative phase transitions through photon correlations, even when mean-field signatures are washed out by quantum fluctuations.

Findings

Photon bunching signals increase near the transition.

Decay times extend by over nine orders of magnitude.

Liouvillian gap scaling indicates the phase transition.

Abstract

Understanding and characterizing phase transitions in driven-dissipative systems constitutes a new frontier for many-body physics. A generic feature of dissipative phase transitions is a vanishing gap in the Liouvillian spectrum, which leads to long-lived deviations from the steady-state as the system is driven towards the transition. Here, we show that photon correlation measurements can be used to characterize the corresponding critical slowing down of nonequilibrium dynamics. We focus on the extensively studied phenomenon of optical bistability in GaAs cavity-polaritons, which can be described as a first-order dissipative phase transition. Increasing the excitation strength towards the bistable range results in an increasing photon-bunching signal along with a decay time that is prolonged by more than nine orders of magnitude as compared to that of low density polaritons. In the limit of strong polariton interactions leading to pronounced quantum fluctuations, the mean-field bistability threshold is washed out. Nevertheless, the scaling of the Liouvillian gap closing as thermodynamic limit is approached provides a signature of the emerging dissipative phase transition. Our results establish photon correlation measurements as an invaluable tool for studying dynamical properties of dissipative phase transitions without requiring phase-sensitive interferometric measurements.