Hamburg 2009 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 56: Poster IV
Q 56.13: Poster
Donnerstag, 5. März 2009, 16:30–19:00, VMP 9 Poster
Interaction effects in Bose-Fermi mixtures in optical lattices — •Simon Braun1, Sebastian Will1, Thorsten Best1, Ulrich Schneider1, Lucia Hackermüller1, Dirk-Sören Lühmann2, and Immanuel Bloch1 — 1Johannes Gutenberg-Universität Mainz — 2Universität Hamburg
The Bose-Fermi Hubbard model describes a system exhibiting a rich phase diagram depending on the strength of interactions and tunneling, going even beyond conventional condensed-matter physics. Ultracold atoms confined in optical lattices offer a unique tool for a clean realization of this model with adjustable parameters.
In our experiment, we cool bosonic 87Rb and fermionic 40K to simultaneous quantum degeneracy and load them into a blue-detuned optical lattice with a superimposed optical dipole trap. This setup allows for the trapping of various spin state combinations as well as rapid control over their interactions by the use of Feshbach resonances and Raman transitions between different hyperfine states.
A bosonic superfluid in an optical lattice constitutes a macroscopic matter wave with Poissonian occupation number statistics. From the collapse and revival of this wave (Greiner et al., 2002), we are able to extract the bosonic interaction energies with very high precision and observe the influence of a fermionic admixture on both interaction and number statistics. In a many-particle scenario, we find a pronounced asymmetry in the bosonic interference pattern for repulsive and attractive interactions. In the latter case, self-trapping leads to a marked shift in the superfluid to Mott insulator transition. (Best et al., 2008)