Normal mass density of a superfluid Fermi gas at unitarity

TL;DR

This paper calculates the normal mass density of a superfluid Fermi gas at unitarity, highlighting the role of fermionic quasiparticles and comparing theoretical predictions with recent experimental data.

Contribution

It provides a theoretical calculation of the normal mass density near the superfluid transition and compares it with experimental results, suggesting a larger pairing gap than BCS theory predicts.

Findings

Normal mass density dominated by fermionic quasiparticles near transition

Experimental data indicates a larger superfluid gap than BCS predictions

Reasonable agreement between calculated and observed moments of inertia in traps

Abstract

We calculate the normal mass density of a paired Fermi gas at unitarity. The dominant contribution near the superfluid transition is from fermionic quasiparticle excitations, and is thus sensitive to the pairing gap. A comparison with the recent experiment of Sidorenkov et al. suggests that the superfluid gap near the transition temperature is larger than the BCS value, but the data do not permit a quantitative inference of the gap. Calculations of the quenched moment of inertia of a BCS superfluid in a harmonic trap are in reasonable agreement with the earlier experiment of Riedl et al.