Observation of suppressed viscosity in the normal state of 3He due to superfluid fluctuations

Abstract

Evidence of fluctuations in transport have long been predicted in ³He. They are expected to contribute only within 100μK of T_c and play a vital role in the theoretical modeling of ordering; they encode details about the Fermi liquid parameters, pairing symmetry, and scattering phase shifts. It is expected that they will be of crucial importance for transport probes of the topologically nontrivial features of superfluid ³He under strong confinement. Here we characterize the temperature and pressure dependence of the fluctuation signature, by monitoring the quality factor of a quartz tuning fork oscillator. We have observed a fluctuation-driven reduction in the viscosity of bulk ³He, finding data collapse consistent with the predicted theoretical behavior.

Early theoretical work predicted that fluctuations above the superfluid transition in liquid 3He should be observable in viscosity. Baten et al. document the reduction of the viscosity due to fluctuations, by monitoring the quality factor of a resonator immersed in 3He as a function of pressure and temperature.