Berlin 2008 – wissenschaftliches Programm

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SYPT: Symposium Quantum Phase Transitions

SYPT 1: SYPT

SYPT 1.5: Hauptvortrag

Montag, 25. Februar 2008, 16:35–17:10, H 0105

Towards Quantum Magnetism with Ultracold Quantum Gases in Optical Lattices — •Immanuel Bloch — Institut für Physik, Johannes Gutenberg Universität, 55099 Mainz

Quantum mechanical superexchange interactions form the basis of quantum magnetism in strongly correlated electronic media and are believed to play a major role in high-Tc superconducting materials. We report on the first direct measurement of such superexchange interactions with ultracold atoms in optical lattices. After preparing a spin-mixture of ultracold atoms with the help of optical superlattices in an antiferromagnetically ordered state, we are able to observe a coherent superexchange mediated spin dynamics down to coupling energies as low as 5 Hz. Furthermore, it is shown how these superexchange interactions can be fully controlled in magnitude and sign. The prospects of using such superexchange interactions for the investigation of dynamical behaviour in quantum spin systems and for quantum information processing will be outlined in the talk. In addition, we present novel results on the experimentally measured phase diagram of a bosonic quantum gas across the quantum phase transition from a superfluid to a Mott insulator and report on results of strongly interacting Bose-Fermi and Fermi-Fermi mixtures in a three-dimensional optical lattice.