The effect of boson-boson interaction on the Bipolaron formation

TL;DR

This paper investigates how boson-boson interactions influence bipolaron formation in ultra-cold Bose gases, highlighting limitations of standard methods and proposing improvements via the Born-Oppenheimer approximation.

Contribution

It introduces a mean-field approach within the Born-Oppenheimer approximation to better account for boson-boson interactions in bipolaron formation.

Findings

Standard linearization methods are valid only in weak coupling and large impurity separations.

Inclusion of boson-boson interactions at the mean-field level improves modeling accuracy.

The approach extends the validity of bipolaron analysis to stronger coupling regimes.

Abstract

Impurities immersed into a surrounding ultra-cold Bose gas experience interactions mediated by the surrounding many-body environment. If one focuses on two impurities that are sufficiently close to each other, they can form a bipolaron pair. Here, we discuss how the standard methods based on linearizing the condensate field lead to results only valid in the weak coupling regime and for sufficiently large impurity separations. We show how those shortcomings can be remedied within the Born-Oppenheimer approximation by accounting for boson-boson interactions already on the mean-field level.