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TT: Fachverband Tiefe Temperaturen

TT 34: Postersession Matter at Low Temperature: Quantum Liquids, Bose-Einstein Condensates, Ultra-Cold Atoms

TT 34.4: Poster

Mittwoch, 25. März 2009, 14:00–18:00, P1A

Bosonic Dynamical Mean Field Theory for the Bose-Hubbard model
— •Andreas Huberer, Michiel Snoek, and Walter Hofstetter — Institut für Theoretische Physik, J. W. Goethe-Universität, D-60438 Frankfurt, Germany

We study the physics of strongly correlated bosonic particles in optical lattices. The conventional bosonic Gutzwiller approximation, in which the hopping is treated in mean field, is exact in infinite dimensions and qualitatively reproduces the phase diagram. However, it does not include the effect of the hopping of normal particles and underestimates the size of the Mott insulating domains. We therefore take into account the leading 1/z corrections (z being the lattice coordination number) to the Gutzwiller approximation, which corresponds to Bosonic Dynamical Mean Field Theory. We derive the self-consistency relations for the superfluid order parameter and the Green’s function. In order to solve them we use Exact Diagonalization as an impurity solver. Using this method we calculate the phase diagram for a single species of bosons at zero and nonzero temperature and calculate corrections to the mean-field results for various quantities. Furthermore we investigate the phase diagram for a mixture of two different spin states with unit filling at both zero and nonzero temperature. We apply this model to the experimental relevant case of a Rubidium-Potassium-mixture.