Observation of suppressed viscosity in the normal state of ${}^3$He due to superfluid fluctuations

Abstract

By monitoring the quality factor of a quartz tuning fork oscillator we have observed a fluctuation-driven reduction in the viscosity of bulk ${}^3$He in the normal state near the superfluid transition temperature, $T_c$. These fluctuations, which are only found within $100\mu$K of $T_c$, play a vital role in the theoretical modeling of ordering; they encode details about the Fermi liquid parameters, pairing symmetry, and scattering phase shifts. They will be of crucial importance for transport probes of the topologically nontrivial features of superfluid ${}^3$He under strong confinement. Here we characterize the temperature and pressure dependence of the fluctuation signature, finding data collapse consistent with the predicted theoretical behavior.

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