Two impurities in a Bose-Einstein condensate: from Yukawa to Efimov attracted polarons

TL;DR

This paper explores how two impurities in a Bose-Einstein condensate can exhibit both Yukawa and Efimov mediated interactions, leading to the formation of bipolarons and Efimov trimers, with potential observation in ultracold atom experiments.

Contribution

It demonstrates the transition from Yukawa to Efimov interactions in impurity-boson systems within a BEC, revealing new bound states and interaction regimes.

Findings

Weak impurity-boson attraction leads to Yukawa-mediated polarons.

Resonant impurity-boson attraction results in Efimov-bound bipolarons.

Evidence of these phenomena could be observed in ultracold atom mixtures.

Abstract

The well-known Yukawa and Efimov potentials are two different mediated interaction potentials. The first one arises in quantum field theory from the exchange of virtual particles. The second one is mediated by a real particle resonantly interacting with two other particles. This Letter shows how two impurities immersed in a Bose-Einstein condensate can exhibit both phenomena. For a weak impurity-boson attractive interactionattraction with the condensate, the two impurities form two polarons that interact through a weak Yukawa attraction mediated by virtual excitations. For a resonant attraction with the condensate, the exchanged excitation becomes a real boson and the mediated interaction changes to a strong Efimov attraction that can bind the two polarons. The resulting bipolarons turn into in-medium Efimov trimers made of the two impurities and one boson. Evidence of this physics could be seen in ultracold mixtures of atoms.