Quantum droplets of dipolar mixtures

TL;DR

This paper explores the rich phase behavior of two-component dipolar Bose-Einstein condensates, revealing new ground states and the role of quantum fluctuations, with implications for ultra-dilute quantum liquids and impurity physics.

Contribution

It introduces the phase diagram of self-bound dipolar mixtures, highlighting the existence of three ground-state phases and the formation of droplet molecules due to non-local attraction.

Findings

Identification of three ground-state phases: miscible, symmetric immiscible, asymmetric immiscible.

Discovery of droplet molecules formed by immiscible dipolar components.

Quantum fluctuations significantly influence impurity miscibility.

Abstract

Recently achieved two-component dipolar Bose-Einstein condensates open exciting possibilities for the study of mixtures of ultra-dilute quantum liquids. While non-dipolar self-bound mixtures are necessarily miscible with an approximately fixed ratio between the two densities, the density ratio for the dipolar case is free. As a result, self-bound dipolar mixtures present qualitatively novel and much richer physics, characterized by three possible ground-state phases: miscible, symmetric immiscible and asymmetric immiscible, which may in principle occur at any population imbalance. Self-bound immiscible droplets are possible due to mutual non-local inter-component attraction, which results in the formation of a droplet molecule. Moreover, our analysis of the impurity regime, shows that quantum fluctuations in the majority component crucially modify the miscibility of impurities. Our work opens intriguing perspectives for the exploration of spinor physics in ultra-dilute liquids, which should resemble to some extent that of 4He-3He droplets and impurity-doped helium droplets.