Hamburg 2009 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 30: Poster II
Q 30.14: Poster
Tuesday, March 3, 2009, 16:30–19:00, VMP 9 Poster
Fermionic quantum gases with tunable interactions in optical lattices — •Ulrich Schneider, Lucia Hackermüller, Thorsten Best, Sebastian Will, Simon Braun, and Immanuel Bloch — Johannes Gutenberg-Universität Mainz
Mixtures of ultracold fermionic atoms in optical lattices can serve as a tool to test theoretical models of condensed matter physics, a prominent example being the Fermi-Hubbard-Hamiltonian. A Feshbach resonance can be used to control the interaction between the atoms and allows us to explore both the repulsive and the attractive side of the Hubbard model.
In the experiment we sympathetically cool 87Rb and 40K in an optically plugged quadrupole trap followed by an optical dipole trap and reach temperatures of 0.15 T/TF for a 40K spin mixture in F=9/2: mF=-9/2 and mF=-7/2. The combination of a blue-detuned optical lattice with a red-detuned dipole trap enables us to vary the trapping potential and the lattice depth independently, thereby giving us direct control over the central filling factor.
For repulsive interactions we show how the system evolves from compressible, metallic states to Mott-insulating and finally band-insulating states for increasing harmonic confinements. In the case of attractive interactions we observe a counter-intuitive increase in cloud size for strong interactions, which can be explained by a strong decrease of the entropy capacity. In addition, we present new measurements of the formation dynamics and mobility of doublons in the optical lattice.