2021/05/31 by Jiaxun Hou, Thomas Schäfer, Thomas Schaefer
Physics and Astronomy · #Atomic and Subatomic Physics Research #Cold Atom Physics and Bose-Einstein Condensates #Condensed matter physics #Dissipative system #Equation of state #Fermi Gamma-ray Space Telescope #Fermi gas #Mathematical physics #Physics #Quantum mechanics #Quantum, superfluid, helium dynamics #Superfluidity #Unitary state #cond-mat.quant-gas #nucl-th
paper · pdf · doi:10.1103/physreva.104.023313
published as Phys. Rev. A 104, 023313 (2021) · 30 pages, 11 figures. To appear in Phys Rev A
arxiv created 2021/08/01 · openalex publication_date 2021/08/13 · arxiv updated 2021/08/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
In this work we establish constraints on the temperature dependence of the shear viscosity \ensuremathη in the superfluid phase of a dilute Fermi gas in the unitary limit. Our results are based on analyzing experiments that measure the aspect ratio of a deformed cloud after release from an optical trap. We discuss how to apply the two-fluid formalism to the unitary gas and provide a suitable parametrization of the equation of state. We show that in expansion experiments the difference between the normal and superfluid velocities remains small and can be treated as a perturbation. We find that expansion experiments favor a shear viscosity that decreases significantly in the superfluid regime. Using an exponential parametrization, we find \ensuremathη(Tc/2TF)\ensuremath\lesssim0.37[\ensuremathη(Tc/TF)], where Tc is the critical temperature and TF is the local Fermi temperature of the gas.