Hannover 2010 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 58: Quantum Gases: Lattices II

Q 58.7: Talk

Friday, March 12, 2010, 12:00–12:15, E 001

Probing superfluids in optical lattices by momentum-resolved Bragg spectroscopy — •Sören Götze, Philipp T. Ernst, Jasper S. Krauser, Jannes Heinze, Malte Weinberg, Christoph Becker, and Klaus Sengstock — Universität Hamburg, Institut für Laser-Physik, Luruper Chaussee 149, 22761 Hamburg, Germany

By the creation of ultracold quantum gases in optical lattices, superfluids can be realized over a wide range of tunable parameters, with a continuous connection to the regime of strong correlation. However, for full experimental access and a comprehensive comparison with condensed-matter systems, there is a need for new detection techniques to probe their fundamental behaviour, characterized i.e. by the dynamic structure factor. Here we report on a comprehensive study of superfluids in optical lattices by Bragg spectroscopy and present fully momentum-resolved measurements of the band structure and associated interaction effects at several lattice depths. In addition, we directly study the momentum composition of excitations in this system and observe strong indications for Bogoliubov backscattering[1]. Our measurements demonstrate the applicability and limits of the Bogoliubov theory to describe excitation properties of superfluids in periodic potentials and pave the way for further detailed studies of strongly correlated phases, quantum gas mixtures and novel quantum phases.

[1] P. T. Ernst et al., Probing superfluids in optical lattices by momentum-resolved Bragg spectroscopy, Nature Physics advance online publication, 29.11.2009 (DOI: 10.1038/nphys1476)