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Superfluidity in Fermionic Gases:From Molecular Condensates to Cooper Pairs

Thomas Bourdel

Laboratoire Kastler-Brossel, École Normale Supérieure, Paris

3.00pm, Wednesday 15 December 2004, AR103 Seminar Room, Graduate Research Centre

For some years now, we have been able to cool dilute Fermi gases up to quantum degeneracy. Using diffusion resonances called Feshbach resonances, it is now possible to modify the interaction properties in such a gas and to explore the transition from strongly to weakly interacting regime. In the strongly interacting regime, atoms form dimeric molecules. And at low temperature, this molecular gas can undergo a superfluid phase transition that corresponds to a Bose-Einstein condensation. Starting from a molecular condensate, one can reduce the interaction strength and study the transition to the weakly interacting regime where the N-body ground state is a superfluid BCS phase analogous to what is happening for the electron gas in a superconductor. The transition between the two regimes is nowadays still an open problem in theoretical many body physics.

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