Berlin 2014 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 32: Poster: Quantum gases, ultracold atoms and molecules

Q 32.20: Poster

Mittwoch, 19. März 2014, 16:30–18:30, Spree-Palais

The critical velocity in the BEC-BCS crossover — •Niclas Luick, Kai Morgener, Wolf Weimer, Jonas Siegl, Klaus Hueck, and Henning Moritz — Institut für Laserphysik, Universität Hamburg, D-22761 Hamburg

Ultracold fermionic gases are an ideal model system for the study of quantum many-body phenomena. Of particular interest is superfluidity due to the open questions surrounding high-temperature superconductors in solids. One hallmark property of superfluid systems is the critical velocity below which obstacles can move through the fluid without friction.

The broad Feshbach resonance of fermionic 6Li quantum gases provides the unique possibility to investigate superfluidity over a wide range of interactions. We stir the gas with a red-detuned laser beam as a local density perturbation. Above the critical velocity heating can be observed. We present high-precision measurements of the critical velocity along the BEC-BCS crossover which are in excellent agreement with theoretical predictions. The three-dimensional gas can also be transferred to a single layer of a blue-detuned one-dimensional optical lattice. This opens the opportunity to study superfluidity in two-dimensional systems with interactions very different from the three-dimensional case. The actual state of our measurements as well as an overview of our apparatus will be presented.