Session A43: Focus Session: Strongly Interacting Fermi Gases and the BCS-BEC Crossover I

8:00 AM–10:48 AM, Monday, March 13, 2006
Baltimore Convention Center Room: 346

Sponsoring Unit: DAMOP
Chair: C. Chin, University of Chicago

Abstract ID: BAPS.2006.MAR.A43.3

Abstract: A43.00003 : Properties of the BCS-BEC condensate in the BEC regime

8:24 AM–8:36 AM

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  Jesper Levinsen
  Victor Gurarie
    (University of Colorado at Boulder)

We study a gas of fermions undergoing a wide resonance s-wave BCS-BEC crossover, in the BEC regime at zero temperature. We calculate the chemical potential and the speed of sound of this Bose-condensed gas, as well as the condensate depletion, in the low density approximation. We discuss how higher order terms in the low density expansion can be constructed. We demonstrate that the standard BCS-BEC gap equation is invalid in the BEC regime and is inconsistent with the results obtained here. The low density approximation we employ breaks down in the intermediate BCS-BEC crossover region. Hence our theory is unable to predict how the chemical potential and the speed of sound evolve once the interactions are tuned towards the BCS regime. As a part of our theory, we derive the well known result for the bosonic scattering length diagrammatically and check that there are no bound states of two bosons.

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