Critical Velocity and Dissipation of an ultracold Bose-Fermi Counterflow

TL;DR

This paper investigates the critical velocity and dissipation phenomena in ultracold Bose-Fermi mixtures, revealing how interaction tuning affects superfluid behavior and uncovering a dissipation-induced phase-locking effect.

Contribution

It provides experimental measurements of critical velocity across the BEC-BCS crossover and reports a novel phase-locking effect caused by dissipation in ultracold atomic mixtures.

Findings

Critical velocity varies across the BEC-BCS crossover.

Dissipation induces phase-locking of cloud oscillations.

Observation of a Zeno-like effect in the system.

Abstract

We study the dynamics of counterflowing bosonic and fermionic lithium atoms. First, by tuning the interaction strength we measure the critical velocity vc of the system in the BEC-BCS crossover in the low temperature regime and we compare it to the recent prediction of Castin et al., Comptes Rendus Physique, 16, 241 (2015). Second, raising the temperature of the mixture slightly above the superfluid transitions reveals an unexpected phase-locking of the oscillations of the clouds. We interpret this observation as resulting from a Zeno-like effect induced by dissipation.