Hamburg 2009 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 11: Quantengase: Bosonen im Gitter II
Q 11.3: Vortrag
Montag, 2. März 2009, 17:00–17:15, VMP 6 HS-A
Direct Observation of Multi-Band Physics using Quantum Phase Diffusion in 3D Optical Lattices — •Sebastian Will1, Thorsten Best1, Simon Braun1, Ulrich Schneider1, Lucia Hackermüller1, Dirk-Sören Lühmann2, and Immanuel Bloch1 — 1Johannes Gutenberg-Universität Mainz — 2Universität Hamburg
In recent years ultracold bosonic atoms in optical lattices have proven their potential to simulate quantum systems, that are known from condensed matter physics. This was prominently demonstrated by the realisation of the superfluid to Mott insulator transition and has been theoretically described by the Bose-Hubbard model. Its underlying Hamiltonian is restricted to the single, energetically lowest band. However, recent theoretical studies have emphasized, that the interatomic interaction may bring multi-band effects into play and considerably modify the behaviour of the system. In our experiment we have trapped a Bose-Einstein condensate of 87Rb atoms in a 3D optical lattice with minimal underlying harmonic confinement. Through rapid increase of the lattice depth, we have been able to prepare coherent superpositions of atom number states on each site. While tunnelling is strongly suppressed, the dynamical evolution of the system shows a continuous collapse and revival of the phase of the matterwave field, the period of which is determined by the onsite interaction energy. Up to 80 revivals of the matterwave field have been detectable. The observed dynamics give clear indication of multi-band physics beyond the single-band Hubbard model, our data being in excellent agreement with theoretical calculations obtained with the method of exact diagonalization.