Density-induced processes in quantum gas mixtures in optical lattices

Ole Jürgensen, Klaus Sengstock, and Dirk-Sören Lühmann
Phys. Rev. A 86, 043623 – Published 22 October 2012

Abstract

We show that off-site processes and multiorbital physics have a crucial impact on the phase diagram of quantum gas mixtures in optical lattices. In particular, we discuss Bose-Fermi mixtures where the intra- and interspecies interactions induce competing density-induced hopping processes, the so-called bond-charge interactions. Furthermore, higher bands strongly influence tunneling and on-site interactions. We apply a multiorbital interaction-induced dressing of the lowest band, which leads to renormalized hopping processes. These corrections give rise to an extended Hubbard model with intrinsically occupation-dependent parameters. The resulting decrease of the tunneling competes with a decrease of the total on-site interaction energy, both affecting the critical lattice depth of the superfluid to Mott-insulator transition. In contrast to the standard Bose-Fermi Hubbard model, we predict a large shift of the transition to shallower lattice depths with increasing Bose-Fermi attraction. The applied theoretical model allows an accurate prediction of the modified tunneling amplitudes and the critical lattice depth, both being recently observed experimentally.

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  • Received 17 July 2012

DOI:https://doi.org/10.1103/PhysRevA.86.043623

©2012 American Physical Society

Authors & Affiliations

Ole Jürgensen, Klaus Sengstock, and Dirk-Sören Lühmann

  • Institut für Laser-Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany

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Issue

Vol. 86, Iss. 4 — October 2012

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