Metamorphosis of Goldstone and Soft Fluctuation Modes in Polariton Lasers

TL;DR

This paper investigates the complex behavior of soft fluctuation modes in polariton lasers, revealing their transformation and connection to various physical phenomena through a microscopic theoretical approach.

Contribution

It introduces a comprehensive microscopic theory that describes the transformation of soft modes in polariton lasers across different parameters, unifying multiple physical concepts.

Findings

Identification of exceptional-point Goldstone modes

Unified description of Mott transition, Mollow spectra, and BCS gaps

Rich transformation behavior of soft modes in parameter space

Abstract

For a driven-dissipative quantum many-body system prepared in a spontaneous broken-symmetry steady state, in addition to the Goldstone mode the soft fluctuation modes provide important insight into the system's dynamics. Using a microscopic polariton laser theory, we find a rich transformation behavior of discrete and continuum soft modes in a two parameter (pump density and cavity dissipation rate) space. In addition to finding exceptional-point Goldstone companion modes, our theory yields a unified picture of a variety of seemingly disconnected physical concepts including Mott transition, Mollow spectra or relaxation oscillations, and polaritonic Bardeen-Cooper-Schrieffer gaps.