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KTH/Nordita/SU seminar in Theoretical Physics

Cold atomic gas in an optical lattice: effects of coupling internal atomic states

by Jonas Larson (Nordita)

FB55 (OBS!)

FB55 (OBS!)

In recent years, systems of cold atoms in optical lattices have drawn great interest. Due to their purity and high controllability of system parameters, they provide a salient model for the study of correlated many-body systems. In the milestone experiment by Bloch and co-workers, the first atomic phase transition between a Mott insulator state to a superfluid state was demonstrated. Such a transition derives from an interplay between atom-atom interaction and atomic kinetic energies. In this talk I first consider the ground state of an ideal coupled two-component gas of ultracold atoms in a 1-D optical lattice, either bosons or fermions. In particular, I will show that despite lack of atom-atom interaction a first order phase transition is possible, originating from a competition between internal and external atomic degrees of freedom. In the case of fermions it is argued that the phase transition has a topological character. Secondly, I will consider interacting bosons and outline how coupling of internal atomic states modifies the Mott-superfluid phase diagram.