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TT: Fachverband Tiefe Temperaturen

TT 32: MLT: Quantum Liquids, Bose-Einstein Condensates, Ultra-cold Atoms, ... 2

TT 32.12: Vortrag

Donnerstag, 25. März 2010, 17:15–17:30, H18

Phonon-assisted currents of fermions in Bose--Fermi mixtures — •Martin Bruderer, Anna Posazhennikova, and Wolfgang Belzig — Fachbereich Physik, Universität Konstanz, D-78457 Konstanz, Germany

We present an analysis of Bose--Fermi mixtures in optical lattices for the case where a static force is applied to the fermions, and the bosons (in the superfluid phase) are described by Bogoliubov phonons. Accordingly, the static force lifts the degeneracy of the energy levels in the lattice potential and the fermionic states form a Wannier--Stark ladder. We show that the Bogoliubov phonons enable hopping transitions between different Wannier--Stark states; these transitions are accompanied by energy dissipation into the superfluid and result in a net fermionic current along the lattice. We determine the dependence of the fermionic current on the static force and find that the phonon density of states strongly affects the emergent current. In particular, if the energy splitting between the Wannier--Stark states exceeds the width of the phonon band, then the current is strongly suppressed. This effect should be observable in a realistic experimental set-up.