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We report on recent experiments with an ultracold degenerate Fermi gas of 6Li atoms. We start with Bose-Einstein condensation of Li2 molecules in an optical trap [1]. Using a Feshbach resonance we can then investigate the BEC-BCS crossover where the molecular condensate is transformed into a strongly interacting gas of fermions. We probe the crossover with several methods like measurements of the trapped cloud size [2], collective oscillation excitations [3] and binding energy measurements with radio frequency [4]. In these measurements we have been able to show the existence of a pairing gap [4] on the BCS side of the resonance. This strongly suggests the presence of a superfluid phase on the BCS side of the crossover.
References [1] S. Jochim et al., Science 302, 2103 (2003); Published online 13 November 2003; 10.1126/science.1093280 [2] M. Bartenstein et al., Phys. Rev. Lett. 92, 120401 (2004). [3] M. Bartenstein et al., Phys. Rev. Lett. 92, 203201 (2004). [4] C. Chin et al., Science 305, 1133 (2004); Published online 22 July 2003; |