Current Studies of the BCS-BEC Crossover via Feshbach Resonance

The past decade has seen marked advances in cooling techniques, making possible the realization of Bose-Einstein condensates and degenerate Fermi gases, most no-tably in the alkali gases. In this paper we review the properties of these systems and the experimental techniques which have made them possible. We then dis-cuss the recent use of a Feshbach resonance in Fermi systems, which allows one to move continuously from a loosely bound Bardeen-Cooper-Schrieffer (BCS) limit to a molecular Bose-Einstein condensate (BEC) limit. Finally, we review studies that have demonstrated the emergence of a condensate in both limits, consider the prop-erties of these two limits, and discuss future work which may elucidate the nature of the BCS-BEC crossover. 1