  In the fermionic Hubbard model, doubly occupied states have an exponentially
large lifetime for strong repulsive interactions U. We show that this property
can be used to prepare a metastable s-wave superfluid state for fermionic atoms
in optical lattices described by a large-U Hubbard model. When an initial
band-insulating state is expanded, the doubly occupied sites Bose condense. A
mapping to the ferromagnetic Heisenberg model in an external field allows for a
reliable solution of the problem. Nearest-neighbor repulsion and pair hopping
are important in stabilizing superfluidity.
