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A Bose-Einstein Condensate Immersed in a Fermi Sea

Dr Florian Schreck

Laboratoire Kastler Brossel, Ecole Normale Superieure, Paris

3.30pm, Monday 3 September 2001, Seminar Room (AR103), Graduate Research School

Fermions and Bosons have opposite statistical properties. The Pauli exclusion principle for Fermions leads at low temperatures to the formation of a Fermi sea, where all the lowest energy states are occupied by exactly one atom. For Bosons, by contrast, the Bose enhancement leads to a macroscopic occupation of the groundstate, a Bose-Einstein condensate.

During my talk I will present an experiment that uses sympathetic cooling between the two Lithium isotopes to produce a Bose Einstein condensate in presence of a Fermi sea. The condensate is produced in the lower hyperfine state where the scattering length is positive and small, leading to a stable and one dimensional condensate. The Fermi sea has a degeneracy of T/T_Fermi=0.2 or higher. The simultaneous presence of the bosonic and fermionic degenerate gases makes the comparision of their behaviour easy. In the future, phenomena like phase separation and Cooper pairing may be observable in this system.

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