Localization to delocalization transition in a driven nonlinear cavity array

TL;DR

This paper investigates phase transitions in driven nonlinear cavity arrays, revealing non-equilibrium Mott insulator states and a transition to delocalized phases with unique coherence properties.

Contribution

It introduces a model for driven nonlinear cavity arrays exhibiting non-equilibrium Mott states and characterizes the transition to delocalized phases, highlighting differences from equilibrium systems.

Findings

Identification of non-equilibrium Mott insulating states.

Observation of a transition to a delocalized phase with spontaneous coherence.

Dephasing effects prevent long-range off-diagonal order.

Abstract

We study nonlinear cavity arrays where the particle relaxation rate in each cavity increases with the excitation number. We show that coherent parametric inputs can drive such arrays into states with commensurate filling that form non-equilibrium analogs of Mott insulating states. We explore the boundaries of the Mott insulating phase and the transition to a delocalized phase with spontaneous first order coherence. While sharing many similarities with the Mott insulator to superfluid transition in equilibrium, the phase-diagrams we find also show marked differences. Particularly the off diagonal order does not become long range since the influence of dephasing processes increases with increasing tunneling rates.