Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 1: Focussed Session: The Mott Transition in Model Systems

TT 1.1: Hauptvortrag

Montag, 23. März 2009, 10:15–10:45, HSZ 03

Strongly Correlated Fermionic Quantum Gases in Optical Lattices — •Immanuel Bloch — Institut für Physik, Johannes Gutenberg-Universität, Germany

Mixtures of ultracold quantum gases in optical lattices can act as novel fundamental model system, with which the physics of the Hubbard model can be experimentally tested in a versatile and highly tunable experimental setting. We present experiments on the static and dynamic properties of such strongly interacting fermions in optical lattices and compare these to state of the art calculations using e.g. Dynamical Mean Field Theory (DMFT) in three dimensions. For repulsive interacting degenerate quantum gas mixtures, we find that by increasing the interactions between the particles, the system can be tuned from a metal over a Mott insulator into a band insulator for increasing compression of the quantum gas. We have implemented a novel detection method that can directly measure the resulting compressibility of these interacting fermionic many-body systems. For increasingly attractive interactions, we find that beyond a critical interaction strength between the particles the gas expands rather than contracts. Such an anomalous spatial expansion is intimately linked to the formation of attractively bound fermion pairs in the system. Finally, novel experiments on the dynamical expansion of interacting fermions are presented. Such diffusion measurements should allow us to shed new light on the complex interplay of interacting fermions in disordered potentials in the future.