Disorder-assisted excitation localization in chirally coupled quantum emitters

TL;DR

This paper investigates how disorder influences excitation localization in chiral quantum emitter arrays, revealing a phase transition, ergodicity breaking, and entanglement dynamics in open quantum systems.

Contribution

It uncovers the disorder-induced phase transition from delocalization to localization and explores the interplay between decay directionality and dipole interactions in chiral quantum systems.

Findings

Identification of a dynamical phase transition to localization.

Observation of ergodicity breaking in localized phases.

Re-entrant localization behavior driven by interactions.

Abstract

One-dimensional quantum emitters with chiral couplings can exhibit nonreciprocal decay channels, along with light-induced dipole-dipole interactions mediated via an atom-waveguide interface. When the position disorders are introduced to such atomic array, we are able to identify the dynamical phase transition from excitation delocalization to localization, with an interplay between the directionality of decay rates and the strength of light-induced dipole-dipole interactions. Deep in the localization phase, its characteristic length decreases and saturates toward a reciprocal coupling regime, leading to a system dynamics whose ergodicity is strongly broken. We also find an interaction-driven re-entrant behavior of the localization phase and a reduction of level repulsion under strong disorder. The former coincides with a drop in the exponent of power-law decaying von Neumann entropy, which gives insights to a close relation between the preservation of entanglement and nonequilibrium dynamics in open quantum systems, while the latter presents a distinct narrow distribution of gap ratios in this particular disordered system.