Fermion-mediated BCS-BEC crossover in ultracold potassium-40 gases

Meera Parish

Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UK

Feshbach resonance phenomena in atomic Fermi gases involves the multiple scattering of atoms from open channel states into a molecular bound state formed from neighbouring closed channel states. Current theories treat the closed channel molecule as a featureless boson, but it can be argued that this interpretation is inappropriate when applied to potassium-40, since the molecule shares a hyperfine spin state with the open channel states. Within the context of a 3-fermion model, where a fermion is shared between the open and closed channel states, we explore the integrity of Feshbach resonance phenomena and assess the extent to which the nature of the bound state impinges on the mean-field characteristics of the system.