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- Title
Strong-Coupling Effects and Shear Viscosity in an Ultracold Fermi Gas.
- Authors
Kagamihara, D.; Ohashi, Y.
- Abstract
We theoretically investigate the shear viscosity $$\eta $$ , as well as the entropy density s, in the normal state of an ultracold Fermi gas. Including pairing fluctuations within the framework of a T-matrix approximation, we calculate these quantities in the Bardeen-Cooper-Schrieffer (BCS)-Bose-Einstein condensation (BEC) crossover region. We also evaluate $$\eta / s$$ , to compare it with the lower bound of this ratio, conjectured by Kovtun, Son, and Starinets (KSS bound). In the weak-coupling BCS side, we show that the shear viscosity $$\eta $$ is remarkably suppressed near the superfluid phase transition temperature $$T_{\mathrm{c}}$$ , due to the so-called pseudogap phenomenon. In the strong-coupling BEC side, we find that, within the neglect of the vertex corrections, one cannot correctly describe $$\eta $$ . We also show that $$\eta / s$$ decreases with increasing the interaction strength, to become very close to the KSS bound, $$\hbar /4\pi k_{\mathrm{B}}$$ , on the BEC side.
- Subjects
ELECTRON gas; VISCOSITY; SHEAR (Mechanics); ENTROPY; FLUCTUATIONS (Physics); T-matrix; BOSE-Einstein condensation
- Publication
Journal of Low Temperature Physics, 2017, Vol 187, Issue 5/6, p692
- ISSN
0022-2291
- Publication type
Article
- DOI
10.1007/s10909-017-1770-6