The BEC/BCS Crossover in an Atomic Gas Randall G. Hulet, Fayez Sarofim Professor of Physics, Rice University, Houston, TX

Recent progress in cooling atomic Fermi gases has demonstrated their ability to realize some of the paradigm models of condensed matter physics. Many of the parameters of trapped atomic gases, including their density, temperature, and interaction strength and sign, can all be controlled with high precision. I will discuss the cooling of an atomic Fermi gas of 6Li atoms to quantum degeneracy and the realization of a strongly interacting Fermi gas by use of a magnetically-tunable collisional “Feshbach” resonance. We have created a Bose-Einstein condensate (BEC) of atomic pairs and have used the condensate as a starting point to explore the BEC/BCS crossover that occurs at the Feshbach resonance. Optical molecular spectroscopy was used to measure the local pair correlations in both the BEC and the BCS regimes. This technique provides a quantitative measurement of the microscopic physics of the Feshbach-induced pairs.