Dissipation-driven quantum phase transitions in collective spin systems

TL;DR

This paper explores how strong dissipation can induce both continuous and discontinuous quantum phase transitions in collective spin systems, analyzing entanglement and bistability near critical points.

Contribution

It demonstrates the occurrence of both first- and second-order dissipative quantum phase transitions in two collective spin models, with detailed entanglement analysis.

Findings

Second-order phase transition in cooperative resonance fluorescence.

First- and second-order transitions in dissipative Lipkin-Meshkov-Glick model.

Maximum entanglement near critical points.

Abstract

We consider two different collective spin systems subjected to strong dissipation -- on the same scale as interaction strengths and external fields -- and show that either continuous or discontinuous dissipative quantum phase transitions can occur as the dissipation strength is varied. First, we consider a well known model of cooperative resonance fluorescence that can exhibit a second-order quantum phase transition, and analyze the entanglement properties near the critical point. Next, we examine a dissipative version of the Lipkin-Meshkov-Glick interacting collective spin model, where we find that either first- or second-order quantum phase transitions can occur, depending only on the ratio of the interaction and external field parameters. We give detailed results and interpretation for the steady state entanglement in the vicinity of the critical point, where it reaches a maximum. For the first-order transition we find that the semiclassical steady states exhibit a region of bistability.