Counterflow in a doubly superfluid mixture of Bosons and Fermions

TL;DR

This paper investigates the frictional interactions in a mixture of bosonic and fermionic superfluids, deriving relations to their dynamical structure factors and analyzing damping behaviors near critical velocities.

Contribution

It introduces a mean-field based calculation of friction between counter-flowing superfluids and relates it to the fermionic dynamical structure factor, providing asymptotic expressions for different interaction regimes.

Findings

Friction force relates to the fermionic dynamical structure factor.

Asymptotic expressions derived for weakly and strongly attractive fermions.

Damping rate follows simple scaling laws near the critical velocity.

Abstract

In this article, we calculate the friction between two counter-flowing bosonic and fermionic super-fluids. In the limit where the boson-boson and boson-fermion interactions can be treated within the mean-field approximation, we show that the force can be related to the dynamical structure factor of the fermionic component. Finally, we provide asymptotic expressions for weakly and strongly attractive fermions and show that the damping rate obeys simple scaling laws close to the critical velocity.