Superfluid Precursor Effects in a Model of Hybridized Bosons and Fermions

We examine how a superfluid state is approached in a system of localizedbosons (tightly bound electron pairs) in contact with a reservoir of itinerantfermions (electrons). Assuming spontaneous decay and recombination betweenthese two species, the initially localized states of the bosons change overinto free-particle–like propagating statesas the temperature is lowered and the superfluid transition at $T_c$ is approached. Concomitantly a pseudogap opens up in the fermionic density of states which deepens with decreasing temperature.