Long-range interactions and symmetry-breaking in quantum gases through optical feedback

TL;DR

This paper explores how optical feedback from a mirror induces long-range interactions in a quasi-2D Bose-Einstein condensate, leading to novel ground states like self-bound quantum droplets, with experimental feasibility demonstrated.

Contribution

It introduces a new mechanism for effective long-range interactions in quantum gases via optical feedback, resulting in unique ground states not previously observed.

Findings

Formation of self-bound quantum droplets

Spontaneous contraction into one-dimensional chains

Feasibility of experimental observation

Abstract

We consider a quasi two-dimensional atomic Bose Einstein condensate interacting with a near-resonant laser field that is back-reflected onto the condensate by a planar mirror. We show that this single-mirror optical feedback leads to an unusual type of effective interaction between the ultracold atoms giving rise to a rich spectrum of ground states. In particular, we find that it can cause the spontaneous contraction of the quasi two-dimensional condensate to form a self-bound one-dimensional chain of mesoscopic quantum droplets, and demonstrate that the observation of this exotic effect is within reach of current experiments.