Fermion-Mediated BCS-BEC Crossover in Ultracold 40K Gases

Studies of Feshbach resonance phenomena in fermionic alkali gases have drawn heavily on the intuition afforded by a Fermi-Bose theory which presents the Feshbach molecule as a featureless Bose particle. While this model may provide a suitable platform to explore the 6Li system, we argue that its application to 40K, where the hyperfine structure is inverted, is inappropriate. Introducing a three-state Fermi model, where a spin state is shared by the open and closed channel states, we show that effects of 'Pauli blocking' appear in the internal structure of the condensate wave function