The Bose polaron problem: effect of mass imbalance on binding energy

TL;DR

This study uses Quantum Monte Carlo methods to analyze how mass imbalance affects the binding energy of a Bose polaron at zero temperature, providing theoretical insights and comparisons with experiments.

Contribution

It offers a detailed quantum Monte Carlo analysis of the Bose polaron binding energy considering mass imbalance, including a universal case and experimental comparison.

Findings

Binding energy depends on mass ratio and interaction strength.

Universal behavior observed for static impurity case.

Good agreement with recent experimental data.

Abstract

By means of Quantum Monte Carlo methods we calculate the binding energy of an impurity immersed in a Bose-Einstein condensate at T = 0. The focus is on the attractive branch of the Bose polaron and on the role played by the mass imbalance between the impurity and the surrounding particles. For an impurity resonantly coupled to the bath, we investigate the dependence of the binding energy on the mass ratio and on the interaction strength within the medium. In particular, we determine the equation of state in the case of a static (infinite mass) impurity, where three-body correlations are irrelevant and the result is expected to be a universal function of the gas parameter. For the mass ratio corresponding to $^{40}$K impurities in a gas of $^{87}$Rb atoms we provide an explicit comparison with the experimental findings of a recent study carried out at JILA.