Heidelberg 2015 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 70: Ultracold Atoms, Ions and BEC V (with A)
Q 70.1: Talk
Friday, March 27, 2015, 11:00–11:15, M/HS1
Probing superfluidity of Bose-Einstein condensates via stirring — •Vijay Pal Singh1,2, Wolf Weimer2, Kai Morgener2, Jonas Siegl2, Klaus Hueck2, Niclas Luick2, Henning Moritz2, and Ludwig Mathey1,2 — 1Zentrum für Optische Quantentechnologien, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany — 2Institut für Laserphysik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
We investigate the superfluid behavior of a Bose-Einstein condensate of 6Li molecules. In the experiment the condensate is stirred by a small attractive potential along a circular path. The moving potential produces almost no heating when its velocity is below the critical velocity vc. The rate of induced heating increases steeply above vc. The observed critical velocity, however, is smaller than the Bogoliubov speed of sound. To understand this, we perform numerical simulations and identify the factors that reduce vc. The critical velocity is influenced by the finite temperature, the inhomogeneous density along the strongly confined direction, the circular instead of linear motion of the stirring potential, and the finite depth of the potential. The simulated critical velocities with experimental parameters are in excellent agreement with the experimentally measured ones.