Construction of a giant vortex state in a trapped Fermi system

TL;DR

This paper explores the formation of giant vortex states in trapped superfluid Fermi gases with anharmonic potentials, highlighting the conditions for superfluidity and unique density features.

Contribution

It introduces a model for giant vortex states in anharmonic traps and analyzes the effects of angular momentum-dependent interactions on superfluid properties.

Findings

Superfluidity exists in the interior of the toroidal density distribution.

Pairing interactions are strongest near the energy minimum, not just at the Fermi level.

Localized density depressions can arise due to pairing effects.

Abstract

A superfluid atomic Fermi system may support a giant vortex if the trapping potential is anharmonic. In such a potential, the single-particle spectrum has a positive curvature as a function of angular momentum. A tractable model is put up in which the lowest and next lowest Landau levels are occupied. Different parameter regimes are identified and characterized. Due to the dependence of the interaction on angular momentum quantum number, the Cooper pairing is at its strongest not only close to the Fermi level, but also close to the energy minimum. It is shown that the gas is superfluid in the interior of the toroidal density distribution and normal in the outer regions. Furthermore, the pairing may give rise to a localized density depression in configuration space.