Heidelberg 2015 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 69: Ultracold Atoms and Molecules (with A)

Q 69.2: Talk

Friday, March 27, 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 [1]. 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: [1] Grossert et al., arXiv:1407.0605 (2014)