Darmstadt 2008 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 47: Quantengase (Bosonen II / Fermionen)
Q 47.8: Talk
Thursday, March 13, 2008, 18:15–18:30, 1A
Finite-Temperature Collective Dynamics of a strongly interacting Fermi Gas — •Christoph Kohstall1, Stefan Riedl1,2, Edmundo R. Sánchez Guajardo1, Alexander Altmeyer1,2, Johannes Hecker Denschlag1, and Rudolf Grimm1,2 — 1Inst. of Experimental Physics and Center for Quantum Physics, Univ. Innsbruck, 6020 Innsbruck, Austria — 2Inst. for Quantum Optics and Quantum Information, Acad. of Science, 6020 Innsbruck, Austria
Collective excitations are a powerful tool to investigate the dynamics of a strongly interacting fermionic quantum gas.
In a weakly interacting Bose gas hydrodynamic behavior coincides with superfluidity. According to BCS-theory superfluidity of fermions concurs with pairing. These two predictions are no more valid in the BEC-BCS crossover where interactions are strong; hydrodynamic behavior, superfluidity and pairing are established at different temperatures.
The focus of this talk is our experimental data on collective oscillations of an ultracold, strongly interacting gas of 6Li atoms showing the transition from hydrodynamic to nearly collisionless behavior as a function of temperature. The results are in agreement with recent calculations that take into account Pauli blocking and pairing.
We find a novel feature of the scissors mode which might indicate the critical temperature for superfluidity.
In addition, radiofrequency spectra reveal the existence of atom pairs up to a temperature where the gas behaves nearly collisionless.