Dissipative phase transitions: Independent versus collective decay and spin squeezing

TL;DR

This paper investigates how different types of dissipation affect phase transitions in the XY model with infinite-range interactions, revealing distinct behaviors and the potential for infinite spin squeezing under collective decay.

Contribution

It demonstrates that independent and collective decay cause different types of phase transitions in the steady state of the model, and shows how drive can induce infinite spin squeezing.

Findings

Independent decay causes a second-order phase transition to ferromagnetism.

Collective decay results in a first-order transition to a time-dependent phase.

Drive induces infinite spin squeezing in the thermodynamic limit.

Abstract

We study the XY model with infinite-range interactions (Lipkin-Meshkov-Glick model) in the presence of dissipation from spontaneous decay. We show that independent and collective decay lead to qualitatively different phase transitions of the steady state, even though the phase boundary is the same. Independent decay leads to a second-order phase transition to a ferromagnet, while collective decay leads to a first-order transition to a time-dependent oscillatory phase. Then we show that the addition of a drive leads to infinite spin squeezing for collective decay in the thermodynamic limit. Our results can be experimentally seen in trapped-ion and cavity-QED experiments.