Dilute quantum liquid in a K-Rb Bose mixture

TL;DR

This paper investigates a dilute quantum liquid formed in a K-Rb Bose mixture, validating the Lee-Huang-Yang correction near the gas-liquid transition and comparing different energy functionals to analyze stability and surface properties.

Contribution

It provides a systematic comparison of energy functionals for a heteronuclear Bose mixture, validating the Lee-Huang-Yang correction and exploring stability and surface characteristics.

Findings

Lee-Huang-Yang correction is valid near the gas-liquid transition

Extended energy functionals improve accuracy of bulk property predictions

Surface tension and other properties depend on inter-species interaction strength

Abstract

A quantum liquid in a heterogeneous mixture of $^{41}$K and $^{87}$Rb atoms is studied using the diffusion Monte Carlo method and Density Functional Theory. The perturbative Lee-Huang-Yang term for a heterogeneous mixture is verified and it is proved to be valid only near the gas-liquid transition. Based on the equations of state of the bulk mixture, calculated with diffusion Monte Carlo, extensions to Lee-Huang-Yang corrected mean-field energy functionals (MF+LHY) are presented. Using Density Functional Theory, a systematic comparison between different functionals is performed, focusing on the critical atom number, surface tension, surface width, Tolman length, and compressibility. These results are given as a function of the inter-species interaction strength, within the stability domain of the liquid mixture.