Dynamically generated double occupancy as a probe of cold atom systems

The experimental investigation of quantum phases in optical lattice systems provides major challenges. Recently, dynamical generation of double occupancy via modulation of the hopping amplitude t has been used to characterize the strongly correlated phase of fermionic atoms. Here, we want to validate this experimental technique with a theoretical study of the driven Hubbard model using analytic methods. We find that conclusive evidence for a Mott phase can be inferred from such a measurement, provided that sufficiently low temperatures k_{B}T<<t can be reached.

Metastable superfluidity of repulsive fermionic atoms in optical lattices

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.