Superfluidity of an atomic Fermi gas near the unitarity limit

We show that the thermodynamic properties of an atomic Fermi gas near the unitarity limit for Feshbach scattering is not universal as long as the resonance is narrow on the scale of the Fermi energy. In view of ongoing quantum Monte Carlo simulations, we explore this behavior within a mean-field approach extended to a finite temperature by means of a model potential, which allows for a tuning of the scattering phase shift and its energy dependence. Our results may be relevant for constructing a complete theoretical description of the crossover from a Bose–Einstein condensation (BEC) of composite bosons to a Bardeen–Cooper–Schrieffer (BCS) of Cooper pair