Dressed molecules in an optical lattice

Abstract

We present the theory of an atomic gas in an optical lattice near a Feshbach resonance. We derive from first principles a generalized Hubbard model that incorporates all the relevant two-body physics exactly, except for the background atom–atom scattering. For most atoms, the background interactions are negligible, but this is not true for 6Li, which has an exceptionally large background scattering length near the experimentally relevant Feshbach resonance at 834 G. Therefore, we show how to include background atom–atom scattering by solving the on-site two-body Feshbach problem exactly. We apply the obtained solution to 6Li and find that the background interactions indeed have a significant effect in this case.