Suppressing and restoring the Dicke superradiance transition by dephasing and decay

TL;DR

This paper investigates how dephasing destroys the Dicke superradiance transition, but individual decay can restore it, providing an exact solution method and confirming the effects in the thermodynamic limit.

Contribution

It introduces an exact polynomial-scaling solution for the N-atom Dicke model with dephasing and decay, demonstrating the destruction and restoration of superradiance transition.

Findings

Dephasing destroys the superradiance transition.

Adding decay restores the superradiance transition.

The effects are confirmed in the thermodynamic limit.

Abstract

We show that dephasing of individual atoms destroys the superradiance transition of the Dicke model, but that adding individual decay toward the spin down state can restore this transition. To demonstrate this, we present a method to give an exact solution for the $N$ atom problem with individual dephasing which scales polynomially with $N$. By comparing finite size scaling of our exact solution to a cumulant expansion, we confirm the destruction and restoration of the superradiance transition holds in the thermodynamic limit.