Simple mean-field theory for a zero-temperature fermionic gas at a Feshbach resonance

We present a simple two-channel mean-field theory for a zero-temperature two-component Fermi gas in the neighborhood of a Feshbach resonance. Our results agree with recent experiments on the bare-molecule fraction as a function of magnetic field Partridge, Phys. Rev. Lett. 95, 020404 (2005)]. Even in this strongly coupled gas of 6Li, the experimental results depend on the structure of the molecules formed in the Feshbach resonance and, therefore, are not universal.