Critical velocity for superfluid flow across the BEC-BCS crossover

TL;DR

This paper investigates the critical velocity in a superfluid Fermi gas across the BEC-BCS crossover, revealing a peak at unitarity indicating maximum superfluid robustness, with detailed experimental analysis of dissipation onset.

Contribution

It provides the first detailed experimental measurement of critical velocities across the BEC-BCS crossover, highlighting the peak at unitarity and analyzing effects of lattice depth and density profile.

Findings

Critical velocity peaks at unitarity.

Superfluidity is most robust at resonance.

Dissipation onset correlates with lattice parameters.

Abstract

Critical velocities have been observed in an ultracold superfluid Fermi gas throughout the BEC-BCS crossover. A pronounced peak of the critical velocity at unitarity demonstrates that superfluidity is most robust for resonant atomic interactions. Critical velocities were determined from the abrupt onset of dissipation when the velocity of a moving one dimensional optical lattice was varied. The dependence of the critical velocity on lattice depth and on the inhomogeneous density profile was studied.