Collective excitations of a strongly-correlated non-equilibrium photon fluid across the Mott/superfluid phase transition

TL;DR

This paper develops a Gutzwiller theory for non-equilibrium photon fluids, analyzing collective excitations across the Mott/superfluid transition, with implications for quantum simulation using circuit-QED devices.

Contribution

It introduces a new theoretical framework for non-equilibrium photon fluids and characterizes their collective excitations across phase transitions.

Findings

Identification of diffusive Goldstone mode in superfluid phase

Characterization of particle/hole excitations in Mott insulator

Observable signatures in optical response for experimental detection

Abstract

We develop a Gutzwiller theory for the non-equilibrium steady states of a strongly-interacting photon fluid driven by a non-Markovian incoherent pump. In particular, we explore the collective excitation modes across the out-of-equilibrium Mott/superfluid transition, characterizing the diffusive Goldstone mode in the superfluid phase and the particle/hole excitations in the insulating one. Observable features in the pump-and-probe optical response of the system are highlighted. Our results appear as experimentally accessible to state-of-the-art circuit-QED devices and open the way for driven-dissipative fluids of light as quantum simulators of novel many-body scenarios.