Erlangen 2018 – scientific programme
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A: Fachverband Atomphysik
A 10: Bose-Einstein Condensation (joint session A/Q)
A 10.2: Talk
Monday, March 5, 2018, 14:15–14:30, K 2.016
Second sound across the BEC-BCS crossover — •Vijay Pal Singh1,2,3, Daniel Kai Hoffmann4, Thomas Paintner4, Wolfgang Limmer4, Johannes Hecker Denschlag4, and Ludwig Mathey1,2,3 — 1Zentrum für Optische Quantentechnologien, Universität Hamburg, 22761 Hamburg, Germany — 2Institut für Laserphysik, Universität Hamburg, 22761 Hamburg, Germany — 3The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, Hamburg 22761, Germany — 4Institut für Quantenmaterie, Universität Ulm, 89081 Ulm, Germany
We report on the first and second sound measurements across the BEC-BCS crossover and their theoretical analysis. The measurements are performed in a cigar-shaped three-dimensional cloud of 6Li atoms and molecules. First sound is excited by an external potential that couples to the density, while second sound is excited by a potential modulation resulting mainly in local heating. The velocity of first and second sound is extracted from the propagation of the excited density wave. We find that the second sound velocity is reduced with decreasing cloud density and vanishes at the superfluid-thermal boundary, whereas the first sound velocity is only weakly affected by the cloud density. We compare the experiments on the BEC side of the crossover to numerical simulations and find good agreement.