Polaron bubble stabilised by medium-induced three-body interactions

TL;DR

This paper explores the formation and stability of impurity bubbles within a Bose-Einstein condensate, highlighting the role of medium-induced three-body interactions in stabilizing these structures and predicting observable phenomena in ultracold atomic mixtures.

Contribution

It introduces a new regime where impurities form stable bubbles due to three-body interactions, expanding understanding of impurity behavior in quantum gases.

Findings

Stable impurity bubbles can form due to medium-induced three-body interactions.

A critical interaction strength leads to impurity collapse and bubble ejection.

Possible experimental realization with ultracold atomic mixtures.

Abstract

Mixing two kinds of particles that repel each other usually results in either a homogeneous mixture when the repulsion is weak, or a complete phase separation of the two kinds when their repulsion is too strong. It is shown however that there is an intermediate regime where the two kinds can coexist in their ground state as a bubble immersed in a gas of one kind. Such a situation is obtained by adding heavy repulsive impurities into a Bose-Einstein condensate. Above a certain strength of the mutual repulsion, a stable bubble of impurities and bosons can be formed, resulting from the equilibrium between the interactions induced by the bosons inside the bubble and the outside pressure from the surrounding bosons. At some particular strength, the effective interactions between the impurities consist of only three-body interactions. Finally, above a critical strength, the bosons are ejected from the bubble and the impurities collapse into a pure bubble of impurities. This phenomenon could be observed with an imbalanced mixture of ultra-cold atoms of different masses. Moreover, it appears possible to reach a regime where the impurities form a dense bubble of strongly-interacting particles.