Quantized Superfluid Vortex Rings in the Unitary Fermi Gas

TL;DR

This paper explains the observed slow oscillations in a unitary Fermi gas as quantized vortex rings rather than heavy solitons, using superfluid density functional theory.

Contribution

It provides a new interpretation of experimental observations by modeling them as vortex rings within superfluid DFT, challenging previous soliton-based explanations.

Findings

Oscillations are consistent with vortex rings.

Superfluid DFT accurately reproduces experimental dynamics.

Vortex rings explain the slow oscillation frequencies.

Abstract

In a recent article, Yefsah et al. [Nature 499, 426 (2013)] report the observation of an unusual excitation in an elongated harmonically trapped unitary Fermi gas. After phase imprinting a domain wall, they observe oscillations almost an order of magnitude slower than predicted by any theory of domain walls which they interpret as a "heavy soliton" of inertial mass some 200 times larger than the free fermion mass or 50 times larger than expected for a domain wall. We present compelling evidence that this "soliton" is instead a quantized vortex ring by showing that the main aspects of the experiment can be naturally explained within the framework of time-dependent superfluid DFT.