Heidelberg 2015 – wissenschaftliches Programm
A 40.2: Vortrag
Freitag, 27. März 2015, 11:15–11:30, B/SR
Detecting Floquet resonances with directed transport of ultracold atoms — •Christopher Grossert1, Martin Leder1, Sergey Denisov2, Peter Hänggi2, and Martin Weitz1 — 1Institut für Angewandte Physik,Universität Bonn, Germany — 2Institut für Physik, Universität Augsburg, Germany
The breaking of spatiotemporal symmetry can lead to directed motion in periodically driven systems without any gradients or net forces. To break the relevant symmetries, a biharmonic driving is sufficient in the classical case as well as in the quantum case. For a dissipative system, this so called rocking ratchet system has been studied in previous work. In this talk, we investigate directed transport of ultracold rubidium atoms in a optical realization of a quantum rocking ratchet. By changing parameters of the underlying periodic modulations we resolve transport resonances in the mean momentum of an atomic Bose-Einstein condensate . These resonances are attributed to the avoided crossings between Floquet eigenstates which are widely separated on the energy scale. We observe a bifurcation of a single-peak resonance into a doublet by increasing the amplitude of the drive. Our results prove the feasibility of the fine experimental control over coherent quantum transport in ac-driven optical lattices.
References:  Grossert et al., arXiv:1407.0605 (2014)