Repulsive Fermi Polarons and Their Induced Interactions in Binary Mixtures of Ultracold Atoms

TL;DR

This paper investigates repulsive Fermi polarons in ultracold atom mixtures, analyzing their spectral properties, induced interactions, and entanglement, and proposes a measure to detect these interactions across different atomic systems.

Contribution

It introduces a method to characterize repulsive Fermi polarons and their induced interactions using impurity distance, applicable to various atomic mixtures.

Findings

Spectral broadening indicates induced interactions.

Relative impurity distance measures induced interactions.

Entanglement correlates with interaction strength.

Abstract

We explore repulsive Fermi polarons in one-dimensional harmonically trapped few-body mixtures of ultracold atoms using as a case example a $^6$Li-$^{40}$K mixture. A characterization of these quasiparticle-like states, whose appearance is signalled in the impurity's radiofrequency spectrum, is achieved by extracting their lifetime and residua. Increasing the number of $^{40}$K impurities leads to the occurrence of both single and multiple polarons that are entangled with their environment. An interaction-dependent broadening of the spectral lines is observed suggesting the presence of induced interactions. We propose the relative distance between the impurities as an adequate measure to detect induced interactions independently of the specifics of the atomic mixture, a result that we showcase by considering also a $^6$Li-$^{173}$Yb system. This distance is further shown to be indicative of the generation of entanglement independently of the size of the bath ($^6$Li) and the atomic species of the impurity. The generation of entanglement and the importance of induced interactions are revealed with an emphasis on the regime of intermediate interaction strengths.