5 research outputs found
Resonance effects on the crossover of bosonic to fermionic superfluidity
Feshbach scattering resonances are being utilized in atomic gases to explore
the entire crossover region from a Bose-Einstein Condensation (BEC) of
composite bosons to a Bardeen-Cooper-Schrieffer (BCS) of Cooper pairs. Several
theoretical descriptions of the crossover have been developed based on an
assumption that the fermionic interactions are dependent only on the value of a
single microscopic parameter, the scattering length for the interaction of
fermion particles. Such a picture is not universal, however, and is only
applicable to describe a system with an energetically broad Feshbach resonance.
In the more general case in which narrow Feshbach resonances are included in
the discussion, one must consider how the energy dependence of the scattering
phase shift affects the physical properties of the system. We develop a
theoretical framework which allows for a tuning of the scattering phase shift
and its energy dependence, whose parameters can be fixed from realistic
scattering solutions of the atomic physics. We show that BCS-like nonlocal
solutions may build up in conditions of resonance scattering, depending on the
effective range of the interactions.Comment: 8 pages,7 figure
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