Rotating Fermi gases in an anharmonic trap

TL;DR

This paper investigates the thermodynamic behavior of a rotating polarized Fermi gas in an anharmonic trap, using semiclassical methods to analyze effects of rotation, temperature, and trap shape on the gas's properties and expansion.

Contribution

It introduces a semiclassical expansion approach to study rotating Fermi gases in anharmonic traps, including temperature effects and free expansion analysis, extending understanding beyond prior harmonic trap models.

Findings

Rotating the gas above a critical frequency creates a 'donut'-shaped cloud.

The semiclassical approximation accurately describes experimental conditions.

Temperature influences thermodynamic quantities, with low- and high-temperature regimes analyzed.

Abstract

Motivated by recent experiments on rotating Bose-Einstein condensates, we investigate a rotating, polarized Fermi gas trapped in an anharmonic potential. We apply a semiclassical expansion of the density of states in order to determine how the thermodynamic properties depend on the rotation frequency. The accuracy of the semiclassical approximation is tested and shown to be sufficient for describing typical experiments. At zero temperature, rotating the gas above a given frequency $\Omega_{\rm DO}$ leads to a `donut'-shaped cloud which is analogous to the hole found in two-dimensional Bose-Einstein condensates. The free expansion of the gas after suddenly turning off the trap is considered and characterized by the time and rotation frequency dependence of the aspect ratio. Temperature effects are also taken into account and both low- and high-temperature expansions are presented for the relevant thermodynamical quantities. In the high-temperature regime a virial theorem approach is used to study the delicate interplay between rotation and anharmonicity.