Renormalization group study of Bose polarons

TL;DR

This paper employs the functional renormalization group to analyze Bose polarons, revealing the significance of three-body correlations and providing results that align well with experimental and numerical data.

Contribution

It introduces a renormalization group approach with a derivative expansion ansatz to study impurity energies in Bose gases, emphasizing three-body effects.

Findings

Accurate calculation of attractive and repulsive branch energies

Three-body correlations are crucial for the attractive branch

Results agree well with experiments and simulations

Abstract

We study the properties of a single impurity in a dilute Bose gas, a Bose polaron, using the functional renormalization group. We use an ansatz for the effective action motivated by a derivative expansion, and we compute the energies of the attractive and repulsive branches of excitations in both two and three spatial dimensions. Three-body correlations play an important role in the attractive branch, and we account for those by including three-body couplings between two bath bosons and the impurity. Our calculations compare very favorably with state-of-the-art experimental measurements and numerical simulations.