Universal Quantum Viscosity in a Unitary Fermi Gas

Abstract

A Fermi gas of atoms with resonant interactions is predicted to obey universal hydrodynamics, where the shear viscosity and other transport coefficients are universal functions of the density and temperature. At low temperatures, the viscosity has a universal quantum scale $\hslash n$ where $n$ is the density, while at high temperatures the natural scale is $p_T^3/{\hslash }^2$ where $p_T$ is the thermal momentum. We employ breathing mode damping to measure the shear viscosity at low temperature. At high temperature $T$, we employ anisotropic expansion of the cloud to find the viscosity, which exhibits precise $T^{3/2}$ scaling. In both experiments, universal hydrodynamic equations including friction and heating are used to extract the viscosity. We estimate the ratio of the shear viscosity to the entropy density and compare to that of a perfect fluid.

13 pages, 3 figures

References in corpus (18)

• Many-Body Physics with Ultracold Gases
• Viscosity in Strongly Interacting Quantum Field Theories from Black Hole Physics
• Theory of ultracold Fermi gases
• Vortices and Superfluidity in a Strongly Interacting Fermi Gas
• Observation of the Pairing Gap in a Strongly Interacting Fermi Gas
• Collective excitations of a degenerate gas at the BEC-BCS crossover
• 200 A GeV Au+Au collisions serve a nearly perfect quark-gluon liquid
• On the Strongly-Interacting Low-Viscosity Matter Created in Relativistic Nuclear Collisions
• Viscosity and scale invariance in the unitary Fermi gas
• The potential energy of a ${}^{40}$K Fermi gas in the BCS-BEC crossover
• Measurement of the Entropy and Critical Temperature of a Strongly Interacting Fermi Gas
• Thermodynamic Measurements in a Strongly Interacting Fermi Gas
• The Shear Viscosity to Entropy Density Ratio of Trapped Fermions in the Unitarity Limit
• Shear viscosity and damping for a Fermi gas in the unitarity limit
• Magnetic field control of elastic scattering in a cold gas of fermionic lithium atoms
• Virial theorems for trapped cold atoms
• Is a gas of strongly interacting atomic fermions a nearly perfect fluid?
• Spin diffusion in Fermi gases

Cited by in corpus (2)

• Viscosity and scale invariance in the unitary Fermi gas
• Microscopic Approach to Shear Viscosities in Superfluid Gases: From BCS to BEC