Enhancing the Efimov correlation in Bose polarons with large mass imbalance

TL;DR

This paper investigates how increasing the mass ratio in Bose polarons enhances Efimov physics signatures in the spectral response, revealing observable effects in rf spectra and spectrum broadening due to Efimov-Polaron hybridization.

Contribution

It demonstrates the enhancement of Efimov correlations in Bose polarons with large mass imbalance and analyzes their spectral signatures using a diagrammatic approach up to third order.

Findings

Efimov signatures are amplified with larger mass ratios.

A visible Efimov branch related to the second Efimov trimer is observed.

Boson density tuning leads to hybridization and broadening of the spectrum.

Abstract

We study the effect of Efimov physics (in the few-body sector) to the spectral response of Bose polaron, a many-body system consisting of an impurity immersed in a bath of bosonic atoms. We find that the Efimov correlation can be greatly enhanced by increasing the mass ratio between the bosons and the impurity, which results in visible signatures in the rf spectrum of the polaron. Using a diagrammatic approach up to the third-order virial expansion, we show how the mass imbalance and the enhanced three-body effect modify the line shape and the width of the polaron spectrum. Moreover, we study the effect of a finite boson-boson interaction to the spectrum. Taking the realistic system of Li impurities immersed in Cs bosons with a positive Cs-Cs scattering length, we find a visible Efimov branch, which is associated with the second lowest Efimov trimer, in the polaron spectrum. In particular, by adjusting the boson density the Efimov branch can greatly hybridize with the attractive polaron branch leading to the spectrum broadening near their avoided level crossing. Our results can be directly probed in the cold atoms experiments of Li-Cs and Li-Rb Bose polarons.