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Q: Fachverband Quantenoptik und Photonik
Q 38: Quantengase: Gemische
Q 38.2: Talk
Wednesday, March 4, 2009, 16:45–17:00, VMP 6 HS-A
Self-Trapping of Bosons and Fermions in Optical Lattices — •Dirk-Sören Lühmann1, Kai Bongs2,3, Klaus Sengstock2, and Daniela Pfannkuche1 — 1I. Institut für Theoretische Physik, Universität Hamburg, Germany — 2Institut für Laser-Physik, Universität Hamburg, Germany — 3MUARC, University of Birmingham, UK
Degenerate mixtures of bosonic and fermionic atoms in three-dimensional lattices offer new insight into strongly correlated many-body physics. Already for the single-band Hubbard model, the interplay between interaction and tunneling is reflected in a complex phase diagram. Experimentally, the presence of fermions leads primarily to a reduction of the bosonic superfluidity for attractive interspecies interaction [1-3], which is apparently not covered by ridgid single-band physics. We theoretically investigate [4] the enhanced localization of bosonic atoms allowing for orbital changes and find a self-trapping of the bosons. The fermionic orbitals are substantially squeezed, which results in a strong deformation of the effective potential for bosons. We introduce a renormalized Bose-Hubbard model to predict the critical lattice depth using effective bosonic tunneling and on-site interaction. The results, in general, demonstrate the important role of orbital renormalization and are in good agreement with the recent experiment in Ref. [3], where Feshbach resonances are used to tune the boson-fermion interaction.
[1] K. Günter et al., PRL 96, 180402 (2006). [2] S. Ospelkaus et al., PRL 96, 180403 (2006). [3] Th. Best et al., PRL (in press), arXiv:0807.4504. [4] D.-S. Lühmann et al., PRL 101, 050402 (2008).