Hannover 2010 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 10: Quantum Gases: Bosons II

Q 10.6: Talk

Monday, March 8, 2010, 17:45–18:00, E 001

Cold Atoms in Minibands: Bloch-Zener Oscillations and Band Spectroscopy — •Sebastian Kling, Tobias Salger, Christopher Grossert, and Martin Weitz — Institut für Angewandte Physik, Wegelerstr.8 , 53115 Bonn, Germany

We report on experiments with an atomic ⁸⁷Rb condensate in a biharmonic optical lattice potential. The biharmonic potential is realized with a combination of a standing wave lattice potential of λ /2 spatial periodicity and a lattice of λ /4 periodicity generated by the dispersion of multiphoton Raman transitions. Such lattices allow for realizing a tunable miniband structure for the condensate. Minibands are formed in the band structure if the second band gap is larger than the first one. In this special case the conventional single band approximation for the dynamics is not valid any more and instead a multiband analysis is required. We have investigated experimentally the dynamics of the minibands by observing Bloch-Zener-Oscillations in momentum space. We have furthermore coherently split atomic wavepackets by tunneling at the bandgaps and observed an interference signal after subsequent recombining. This band interference allows for a novel bandgap spectroscopy.