Cavity-induced quantum droplets

TL;DR

This paper predicts the formation of stable quantum droplets in a Bose-Einstein condensate placed in an optical resonator, where cavity-induced long-range interactions and roton modes lead to a self-bound quantum liquid.

Contribution

It introduces a novel mechanism for quantum droplet formation via cavity-induced interactions and demonstrates this with Bogoliubov theory analysis.

Findings

Emergence of a roton mode due to cavity coupling.

Quantum fluctuations stabilize the droplet.

Self-bound quantum liquid forms in the system.

Abstract

Quantum droplets are formed in quantum many-body systems when the competition of quantum corrections with the mean-field interaction yields a stable self-bound quantum liquid. We predict the emergence of a quantum droplet when a Bose-Einstein condensate is placed in an optical resonator with transverse pumping. The strong coupling between the atoms and the cavity mode induces long-range interactions in the atoms and a roton mode for negative cavity detuning emerges. Using a Bogoliubov theory, we show that the roton mode competes with the repulsive atomic $s$-wave scattering. Due to the favorable scaling of the quantum fluctuations with respect to the volume, a self-bound stable quantum liquid emerges.