1. Strong-Coupling Effects and Shear Viscosity in an Ultracold Fermi Gas.
- Author
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Kagamihara, D. and Ohashi, Y.
- Subjects
- *
ELECTRON gas , *VISCOSITY , *SHEAR (Mechanics) , *ENTROPY , *FLUCTUATIONS (Physics) , *T-matrix , *BOSE-Einstein condensation - 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. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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