Shear Viscosity of a Unitary Fermi Gas Near the Superfluid Phase Transition.

Abstract

We measure the shear viscosity for a resonantly interacting Fermi gas as a function of temperature from nearly the ground state through the superfluid phase transition into the high temperature regime. Further, we demonstrate an iterative method to estimate the local shear viscosity coefficient α(S)(θ) versus reduced temperature θ from the cloud-averaged measurements ⟨α(S)⟩, and compare α(S) to several microscopic theories. We find that α(S) reveals features that were previously hidden in ⟨α(S)⟩.