Self-trapping of impurities in Bose-Einstein condensates: Strong attractive and repulsive coupling

TL;DR

This paper investigates how impurities in Bose-Einstein condensates become localized due to interactions, revealing distinct behaviors for attractive versus repulsive impurities and highlighting the impact on BEC density and atom loss.

Contribution

It introduces a Hartree-based analysis of impurity self-trapping in BECs, showing singular ground states for attractive impurities and density enhancements near impurities in lower dimensions.

Findings

Attractive impurities have a singular ground state in 3D.

Density of BEC increases near attractive impurities in 1D and 2D.

Inelastic collisions lead to atom loss and potential impurity loss.

Abstract

We study the interaction-induced localization -- the so-called self-trapping -- of a neutral impurity atom immersed in a homogeneous Bose-Einstein condensate (BEC). Based on a Hartree description of the BEC we show that -- unlike repulsive impurities -- attractive impurities have a singular ground state in 3d and shrink to a point-like state in 2d as the coupling approaches a critical value. Moreover, we find that the density of the BEC increases markedly in the vicinity of attractive impurities in 1d and 2d, which strongly enhances inelastic collisions between atoms in the BEC. These collisions result in a loss of BEC atoms and possibly of the localized impurity itself.