Microscopic Approach to Shear Viscosities in Superfluid Gases: From BCS to BEC

Abstract

We compute the shear viscosity, $\eta$, at general temperatures $T$, in a BCS-BEC crossover scheme which is demonstrably consistent with conservation laws. The study of $\eta$ is important because it constrains microscopic theories by revealing the excitation spectra. The onset of a normal state pairing gap and the contribution from pair degrees of freedom imply that $\eta$ at low $T$ becomes small, rather than exhibiting the upturn predicted by most others. Using the local density approximation, we find quite reasonable agreement with just-published experiments.

arXiv comment4 pages, 2 figures

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• Gauge Invariant Linear Response Theory of Relativistic BCS superfluids
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• Comment on "Density and Spin response of a strongly-interacting Fermi gas in the attractive and quasi-repulsive regime"
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