Dipole oscillation of a trapped Bose--Fermi-mixture gas in collisionless and hydrodynamic regimes

TL;DR

This paper investigates the behavior of dipole oscillations in a trapped Bose-Fermi mixture gas across collisionless and hydrodynamic regimes, revealing mode transitions and damping characteristics using a moment method approach.

Contribution

It introduces a theoretical framework applying the moment method to the Boltzmann equation to analyze dipole modes in Bose-Fermi mixtures across different collisional regimes.

Findings

Collisionless modes crossover to hydrodynamic in-phase modes.

One collisionless mode becomes a damped mode in the hydrodynamic regime.

Dipole mode frequencies depend on temperature.

Abstract

Dipole oscillation is studied in a normal phase of a trapped Bose--Fermi-mixture gas composed of single-species bosons and single-species fermions. Applying the moment method to the linearized Boltzmann equation, we derive a closed set of equations of motion for the center-of-mass position and momentum of both components. By solving the coupled equations, we reveal the behavior of dipole modes in the transition between the collisionless regime and the hydrodynamic regime. We find that two oscillating modes in the collisionless regime have distinct fates in the hydrodynamic regime: one collisionless mode shows a crossover to a hydrodynamic in-phase mode, and the other collisionless mode shows a transition to two purely damped modes. The temperature dependence of these dipole modes are also discussed.