Liquid quantum droplets of ultracold magnetic atoms

TL;DR

This paper explores the formation of quantum droplets in ultracold magnetic atoms, specifically Dysprosium gases, highlighting the role of competing interactions and beyond mean-field effects in creating a new state of matter.

Contribution

It demonstrates the existence of quantum droplets stabilized by a balance of dipolar attraction and quantum fluctuations in dipolar Bose-Einstein condensates.

Findings

Quantum droplets form in Dysprosium gases due to competing interactions.

Long-range dipolar interactions influence the behavior of quantum droplets.

Beyond mean-field effects are crucial for the stability of these droplets.

Abstract

The simultaneous presence of two competing inter-particle interactions can lead to the emergence of new phenomena in a many-body system. Among others, such effects are expected in dipolar Bose-Einstein condensates, subject to dipole-dipole interaction and short-range repulsion. Magnetic quantum gases and in particular Dysprosium gases, offering a comparable short-range contact and a long-range dipolar interaction energy, remarkably exhibit such emergent phenomena. In addition an effective cancellation of mean-field effects of the two interactions results in a pronounced importance of quantum-mechanical beyond mean-field effects. For a weakly-dominant dipolar interaction the striking consequence is the existence of a new state of matter equilibrated by the balance between weak mean-field attraction and beyond mean-field repulsion. Though exemplified here in the case of dipolar Bose gases, this state of matter should appear also with other microscopic interactions types, provided a competition results in an effective cancellation of the total mean-field. The macroscopic state takes the form of so-called quantum droplets. We present the effects of a long-range dipolar interaction between these droplets.