# Coupled Dipole Oscillations of a Mass-Imbalanced Bose and Fermi Superfluid Mixture

## TL;DR

This paper investigates coupled dipole oscillations in a mass-imbalanced Bose-Fermi superfluid mixture, revealing complex frequency shifts and resonance phenomena that challenge existing theories.

## Contribution

It provides high-precision experimental data on coupled oscillations in a Bose-Fermi mixture with large mass imbalance, highlighting novel resonance behaviors.

## Key findings

- Frequency shifts differ between bosonic and fermionic components.
- Resonant-like behavior of frequency shifts near the BCS side.
- Unusual directional dependence of frequency shifts.

## Abstract

Recent experimental realizations of superfluid mixtures of Bose and Fermi quantum gases provide a unique platform for exploring diverse superfluid phenomena. We study dipole oscillations of a double superfluid in a cigar-shaped optical dipole trap, consisting of $^{41}$K and $^{6}$Li atoms with a large mass imbalance, where the oscillations of the bosonic and fermionic components are coupled via the Bose-Fermi interaction. In our high-precision measurements, the frequencies of both components are observed to be shifted from the single-species ones, and exhibit unusual features. The frequency shifts of the $^{41}$K component are upward (downward) in the radial (axial) direction, whereas the $^{6}$Li component has down-shifted frequencies in both directions. Most strikingly, as the interaction strength is varied, the frequency shifts display a resonant-like behavior in both directions, for both species, and around a similar location at the BCS side of fermionic superfluid. These rich phenomena challenge theoretical understanding of superfluids.