Vortices in Superfluid Fermi Gases through the BEC to BCS Crossover

TL;DR

This paper investigates vortex structures in superfluid Fermi gases across the BEC-BCS crossover, revealing how vortex properties and bound states evolve from fermionic to bosonic regimes at zero temperature.

Contribution

It provides a detailed analysis of vortex behavior and bound states in superfluid Fermi gases across the BEC-BCS crossover at T=0, highlighting new features near unitarity.

Findings

Order parameter varies on two scales on the BCS side.

Maximum circulating current occurs near unitarity.

Bound states in vortex cores persist into the BEC regime.

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 $\xi$, while only variation on the scale of $\xi$ is seen away from the BCS limit. The circulating current has a peak value $j_{max}$ which is a non-monotonic function of $1/k_F a_s$ implying a maximum critical velocity $\sim v_F$ at unitarity. The number of fermionic bound states in the core decreases as we move from the BCS to BEC regime. Remarkably, a bound state branch persists even on the BEC side reflecting the composite nature of bosonic molecules.