Vortices in Superfluid Fermi Gases through the BEC to BCS Crossover

Abstract

We have analyzed a single vortex at T=0 in a 3D superfluid atomic Fermi gas across a Feshbach resonance. On the BCS side, the order parameter varies on two scales: k_F^-1 and the coherence length ξ, while only variation on the scale of ξ is seen away from the BCS limit. The circulating current has a peak value j_max which is a nonmonotonic function of 1/k_Fa_s implying a maximum critical velocity ∼vF at unitarity. The number of fermionic bound states in the core decreases as we move from the BCS to the BEC regime. Remarkably, a bound state branch persists even on the BEC side reflecting the composite nature of bosonic molecules.