Spin self-organization in an optical cavity facilitated by inhomogeneous broadening

TL;DR

This paper investigates how inhomogeneous Doppler broadening influences the collective spin self-organization of atoms in an optical cavity, revealing that broadening can facilitate the onset of organized states and lead to complex dynamics.

Contribution

It demonstrates that inhomogeneous broadening, specifically Doppler broadening, can lower the threshold for spin self-organization and induce non-monotonic behavior, a novel insight into light-matter interactions.

Findings

Doppler broadening facilitates spin self-organization.

The threshold for organization is non-monotonic with transition frequency.

Above threshold, complex cooperative dynamics emerge, including density modulations and non-thermal states.

Abstract

We study the onset of collective spin-self-organization in a thermal ensemble of driven two-level atoms confined in an optical cavity. The atoms spontaneously form a spin-pattern above a critical driving strength that sets a threshold and is determined by the cavity parameters, the initial temperature, and the transition frequency of the atomic spin. Remarkably, we find that inhomogeneous Doppler broadening facilitates the onset of spin-self-organization. In particular, the threshold is non-monotonic when increasing the spin transition frequency and reaches a minimum when the Doppler broadening is of similar magnitude. This feature emerges due to Doppler-induced resonances. Above the threshold, we find cooperative dynamics of spin, spatial, and momentum degrees of freedom leading to density modulations, fast reduction of kinetic energy, and the emergence of non-thermal states. More broadly, our work demonstrates how broadening can facilitate strong light-matter interactions in many-body systems.