Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 7: Matter at Low Temperature: Poster Session

TT 7.18: Poster

Montag, 25. Februar 2008, 14:00–18:00, Poster B

Collective dynamics of ultracold atoms in optical lattices — •Michiel Snoek and Walter Hofstetter — J. W. Goethe-Universität, Frankfurt am Main, Deutschland

We analyze the collective dynamics of ultracold atoms in optical lattices induced by a sudden change of the underlying harmonic trapping potential. In order to study the effect of strong interactions, dimensionality and lattice topology on dynamical properties, we consider bosonic atoms with arbitrarily strong repulsive interactions, on a two-dimensional square lattice and a hexagonal lattice. We apply dynamical Gutzwiller mean-field theory.

A shift in the center of the potential invokes dipole oscillations for small amplitudes of the shift. Changing the strenght of the harmonic confinement invokes monopole and quadrupole oscillations. We investigate the frequency of the collective modes as a function of interaction strength and study the coupling and damping of those modes.

Applying a large shift in the center of the potential brings the system far out of equilibrium. We then find insulating behavior for weakly interacting atoms on the square lattice. For strong interactions the center of mass slowly relaxes, even when a Mott plateau is present, which in one dimension blocks the dynamics. On the hexagonal lattice the center of mass relaxes to the new equilibrium position for any interaction strength.