Distinguishing phases using the dynamical response of driven-dissipative light-matter systems

TL;DR

This paper uncovers a unique transition in driven-dissipative light-matter systems triggered by infinitesimal dissipation, characterized by a flip in dynamical fluctuations and linked to exceptional points, with implications for experimental realizations.

Contribution

It reveals a novel transition in the Dicke-Tavis-Cummings model driven by dissipation, highlighting a fluctuation inversion and exceptional point behavior in the dynamical response.

Findings

Dissipation induces a transition between normal phases.

Fluctuations invert from particlelike to holelike across the transition.

Liouvillian eigenvalues exhibit exceptional point characteristics.

Abstract

We present a peculiar transition triggered by infinitesimal dissipation in the interpolating Dicke-Tavis-Cummings model. The model describes a ubiquitous light-matter setting using a collection of two-level systems interacting with quantum light trapped in an optical cavity. In a previous work [Phys. Rev. Lett. 120, 183603 (2018)], dissipation was shown to extend a normal phase (dark state) into new regions of the model's parameter space. Harnessing Keldysh's action formalism to compute the response function of the light, we show that the normal phase does not merely spread but encompasses a transition between the old and the dissipation-stabilized regimes of the normal phase. This transition, however, solely manifests in the dynamical fluctuations atop the empty cavity, through stabilization of an excited state of the closed system. Consequently, we reveal that the fluctuations flip from being particlelike to holelike across this transition. This inversion is also accompanied by the behavior of the Liouvillian eigenvalues akin to exceptional points. Our work forges the way to discovering transitions in a wide variety of driven-dissipative systems and is highly pertinent for current experiments.