Strong-Coupling Effects and Shear Viscosity in an Ultracold Fermi Gas

D. Kagamihara, Yoji Ohashi

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


We theoretically investigate the shear viscosity (Formula presented.), 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 (Formula presented.), 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 (Formula presented.) is remarkably suppressed near the superfluid phase transition temperature (Formula presented.), 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 (Formula presented.). We also show that (Formula presented.) decreases with increasing the interaction strength, to become very close to the KSS bound, (Formula presented.), on the BEC side.

Original languageEnglish
Pages (from-to)1-7
Number of pages7
JournalJournal of Low Temperature Physics
Publication statusAccepted/In press - 2017 Mar 23


  • BCS–BEC crossover
  • Strong-coupling effect
  • Ultracold Fermi gas

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Materials Science(all)
  • Condensed Matter Physics

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