Fluorescence spectrum and thermalization in a driven coupled cavity array

TL;DR

This paper develops a method to compute fluorescence spectra in driven coupled cavity arrays, revealing quasi-thermalization and negative effective temperatures in certain regimes, with analytical and numerical insights.

Contribution

It introduces an extension of correlation evaluation methods for infinite open quantum systems, enabling momentum-resolved fluorescence spectra analysis.

Findings

Identification of quasi-thermalized steady states with temperature dependence

Discovery of negative effective temperature under blue detuned driving

Agreement between numerical results and analytical spin-wave theory

Abstract

We calculate the fluorescence spectra of a driven lattice of coupled cavities. To do this, we extend methods of evaluating two-time correlations in infinite lattices to open quantum systems; this allows access to momentum resolved fluorescence spectrum. We illustrate this for a driven-dissipative transverse field anisotropic XY model. By studying the fluctuation dissipation theorem, we find the emergence of a quasi-thermalized steady state with a temperature dependent on system parameters; for blue detuned driving, we show this effective temperature is negative. In the low excitation density limit, we compare these numerical results to analytical spin-wave theory, providing an understanding of the form of the distribution function and the origin of quasi-thermalization.