Evidence for Superfluidity in a Resonantly Interacting Fermi Gas

TL;DR

This paper presents evidence of superfluid behavior in a resonantly interacting Fermi gas of lithium-6 atoms, demonstrated through collective oscillation measurements that align with superfluid hydrodynamics predictions.

Contribution

It provides the first experimental evidence of superfluid hydrodynamics in a resonantly interacting Fermi gas, challenging previous models based on collisionless or collisional regimes.

Findings

Observed collective oscillations consistent with superfluid hydrodynamics

Damping times and frequencies incompatible with collisionless or collisional models

First evidence of superfluidity in a resonantly interacting Fermi gas

Abstract

We observe collective oscillations of a trapped, degenerate Fermi gas of $^6$Li atoms at a magnetic field just above a Feshbach resonance, where the two-body physics does not support a bound state. The gas exhibits a radial breathing mode at a frequency of 2837(05) Hz, in excellent agreement with the frequency of $\nu_H\equiv\sqrt{10\nu_x\nu_y/3}=2830(20)$ Hz predicted for a {\em hydrodynamic} Fermi gas with unitarity limited interactions. The measured damping times and frequencies are inconsistent with predictions for both the collisionless mean field regime and for collisional hydrodynamics. These observations provide the first evidence for superfluid hydrodynamics in a resonantly interacting Fermi gas.