Temperature-dependent characteristic velocity and excitations of solid helium-4

ORAL

Abstract

Excitations that allow shear velocity to inhibit superflow are well known in superfluids, and typically generate temperature-dependent critical velocities that depend sensitively on the physics of these microscopic dissipative mechanisms. By contrast, the nature of the microscopic excitations associated with the low-temperature {}``supersolid'' inertial anomaly and shear stiffening of solid $^{4}$He remain unknown, and its temperature-dependent characteristic velocity curve $v_{\star}\left(T\right)$ has not yet been observed. Using a SQUID-based torsion oscillator to map the complete complex rotational susceptibility of solid $^{4}$He, we observed that the internal dissipative excitation rates obey power laws of temperature and velocity, and we acquired the full temperature-dependent characteristic velocity function $v_{\star}\left(T\right)$. We compare these observations to the predicted $v_{\star}\left(T\right)$ curves of several microscopic models, including those of a thin-film vortex unbinding and a two-level-system (TLS) momentum deficit.

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Authors

  • Ethan Pratt

    • Cornell University

  • Benjamin Hunt

    • Cornell University

  • Vikram Gadagkar

    • Cornell University

  • Minoru Yamashita

    • Kyoto University

  • Alexander Balatsky

    • Theoretical Division and Center for Integrated Nanotechnology, Los Alamos National Laboratory
    • Los Alamos National Laboratory
    • Theoretical Division and Center for Integrated Nanotechnology, Los Alamos National Laboratory, Los Alamos, NM 87545
    • T-Division, MS B 262, Los Alamos National Lab
    • Los Alamos National Lab

  • J.C. Davis

    • Cornell University
    • Cornell University, Brookhaven National Lab, University of St. Andrews
    • Cornell University, University of St. Andrews, Brookhaven National Laboratory
    • Cornell U., BNL, U. of St. Andrews, U. of British Columbia