Hannover 2010 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 24: Quantum Gases: Mixtures and Spinor Gases

Q 24.8: Vortrag

Mittwoch, 10. März 2010, 12:15–12:30, E 001

Quantum phase diffusion in interacting Bose-Fermi mixtures — •Simon Braun1, Sebastian Will1, Thorsten Best2, Philipp Ronzheimer1, Michael Schreiber1, Ulrich Schneider1, Tim Rom1, Lucia Hackermüller1, Kin-Chung Fong1, Dirk-Sören Lühmann3, and Immanuel Bloch11Ludwig-Maximilians-Universität München — 2ALU Freiburg — 3Universität Hamburg

The system of ultracold bosonic atoms in a 3D optical lattice is commonly described by the Bose-Hubbard model (BHM). While this model only takes into account the lowest Bloch band, theoretical studies indicate that interactions may bring multi-band effects into play.

We have been able to observe and quantify multi-band physics beyond the single-band BHM by studying quantum phase diffusion of a 87Rb BEC in a 3D optical lattice. We observed more than 40 collapses and revivals of the matterwave field, the period of which is determined by the onsite interaction energy. This technique allowed for a precise measurement of interaction energies, being in excellent agreement with theoretical results of a multi-orbital calculation.

In the presence of fermionic 40K atoms, the quantum phase diffusion dynamics show a strong dependence on the interspecies interaction between K and Rb, which can be conveniently tuned via a Feshbach resonance. By driving Raman transitions between Zeeman sublevels we can additionally switch the interspecies interaction almost instantaneously. Our measurements show how interspecies interactions both affect the number statistics in the system and lead to renormalized Hubbard parameters, again revealing multi-band physics in optical lattices.

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