Drag in Bose-Fermi Mixtures

TL;DR

This paper models the drag force experienced by a Bose condensate moving through a Fermi gas, revealing a crossover in scattering regimes and matching experimental results for Cs-Li mixtures.

Contribution

It introduces a kinetic theory model for Bose-Fermi mixtures that captures the crossover between bulk and surface scattering regimes and aligns with experimental data.

Findings

Identification of bulk and surface scattering regimes

Calculation of damping and frequency shifts in dipole modes

Agreement with experimental Cs-Li mixture data

Abstract

We use kinetic theory to model the dynamics of a small Bose condensed cloud of heavy particles moving through a larger degenerate Fermi gas of light particles. Varying the Bose-Fermi interaction, we find a crossover between bulk and surface dominated regimes -- where scattering occurs throughout the Bose cloud, or solely on the surface. We calculate the damping and frequency shift of the dipole mode in a harmonic trap as a function of the magnetic field controlling an inter-species Feshbach resonance. We find excellent agreement between our stochastic model and the experimental studies of Cs-Li mixtures.