Self-bound ultra dilute Bose mixtures within Local Density Approximation

TL;DR

This paper explores the properties and stability conditions of self-bound ultra dilute binary Bose mixtures using Density Functional Theory, providing new insights into their phase behavior, surface tension, and vortex stability.

Contribution

It introduces an explicit Lee-Huang-Yang correction for heteronuclear mixtures and analyzes stability, surface tension, and vortex states within a Local Density Approximation.

Findings

Conditions for stability against evaporation identified

Surface tension varies significantly with inter-species interaction

Droplets can sustain stable vortices and vortex dimers

Abstract

We have investigated self-bound binary ultra dilute bosonic mixtures at zero temperature within Density Functional Theory using a Local Density Approximation. We provide the explicit expression of the Lee-Huang-Yang correction in the general case of heteronuclear mixtures, and investigate the general thermodynamic conditions which lead to the formation of self-bound systems. We have determined the conditions for stability against the evaporation of one component, as well as the mechanical and diffusive spinodal lines. We have also calculated the surface tension of the self-bound state as a function of the inter-species interaction strength. We find that relatively modest changes of the latter result in order-of-magnitude changes in the calculated surface tension. We suggest experimental realizations which might display the metastability and phase separation of the mixture when entering regions of the phase diagram characterized by negative pressures. Finally, we show that these droplets may sustain stable vortex and vortex dimers.