Field-theoretical study of the Bose polaron

TL;DR

This paper investigates the Bose polaron using a field-theoretic approach, predicting spectral and quasiparticle properties, and compares different T-matrix approximations to understand its behavior in a Bose-Einstein condensate.

Contribution

It introduces a field-theoretic framework for analyzing the Bose polaron and compares non-selfconsistent and selfconsistent T-matrix methods for accurate predictions.

Findings

Most spectral weight is in coherent attractive and metastable repulsive branches.

Qualitative behavior is well captured by a non-selfconsistent T-matrix approximation.

Selfconsistent T-matrix accounts for infinite boson excitations from the condensate.

Abstract

We study the properties of the Bose polaron, an impurity strongly interacting with a Bose-Einstein condensate, using a field-theoretic approach and make predictions for the spectral function and various quasiparticle properties that can be tested in experiment. We find that most of the spectral weight is contained in a coherent attractive and a metastable repulsive polaron branch. We show that the qualitative behavior of the Bose polaron is well described by a non-selfconsistent T-matrix approximation by comparing analytical results to numerical data obtained from a fully selfconsistent T-matrix approach. The latter takes into account an infinite number of bosons excited from the condensate.