Seminarvortrag: "Interacting ultracold Fermi-gases in optical lattices"

03 Apr 2009 by Main.RupertHampl in Studium

Einladung zum Seminarvortrag des fakultätsübergreifenden Kooperationszentrums "Functional Matter - Designer Materials and Quantum Technologies" am 6.4., 10 Uhr.

"Interacting ultracold Fermi-gases in optical lattices"
Lucia Hackermüller
Universität Mainz

Ultracold fermionic quantum gases in optical lattices represent a unique model scheme which in principle can be used to simulate complex many-body systems, for example high-Tc superconductors. Similarly to solid state physics, our system is described by the Fermi-Hubbard Hamiltonian with the advantage that all relevant parameters can be controlled with high accuracy. A famous prediction of the Hubbard Hamiltonian is the Mott-insulator, where a metal with half-filled conduction band turns insulating due to interactions.
Experimentally, we prepare a fermionic Mott-insulator with an ultracold repulsively interacting spin mixture of 40K atoms in a blue detuned optical lattice. By measuring the insitu cloud size and its response to an external force - the enclosure of a red detuned optical dipole trap - as well as the number of doubly occupied sites, the insulating and metallic behaviour can be distinguished; and the Mott-insulating regions can be identified. However, changing the interactions to attractive, i.e. studying the attractive Hubbard-Hamiltonian, can lead to surprising effects as well. On tuning the interactions from the repulsive to the attractive side, we find a shrinking followed by an anomalous expansion of the cloud. This unexpected expansion is related to the formation of bound pairs and can be understood as a result of entropy conservation.
Additionally we present measurement on the dynamic response of the system to changes in the external parameters.

Montag, 6. April 2009
10 Uhr

Seminarraum am Atominstitut der Österreichischen Universitäten
Stadionallee 2, 1020 Wien



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Topic revision: r1 - 03 Apr 2009, rupdPHYSIKFHTUFAT

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