Condensed Matter Seminar

Randy Hulet
Rice University

Thursday, November 13, 2008
1:00 pm in SPL 52

Fermion Pairing with Ultracold Atoms

Abstract: Ultracold atomic fermions have the potential for simulating unsolved models of condensed matter physics. In addition to being clean and well-characterized, physical parameters such as interaction strength, temperature, density, and dimensionality are readily tunable. I will discuss experiments on the pairing of 6Li, a composite fermion, where tunable interactions enable the realization of the BEC-BCS crossover. We use optical excitation to an excited molecular state to measure various properties of the paired state, including the local pair correlations, and paired fraction as a function of temperature and interaction around the BEC-BCS crossover. We find the existence of “preformed pairs” far above the critical temperature for superfluidity at the strongly-interacting unitarity limit. We also investigate two-component Fermi gases with unequal spin populations, and find phase separation between a fully paired core and the surrounding unpaired atoms (shown below).