arXiv:0711.0121v3

Vortex Fluid State below an Onset Temperature T0 of Solid 4He

Andrey Penzev, Yoshinori Yasuta, and Minoru Kubota

Institute for solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, 277-8581, Japan

(Dated: February 1, 2008)

Detailed studies of the AC velocity Vac and T dependence of torsional oscillator responses of solid 4He are reported. A characteristic onset temperature T0 ∼ 0.5 K is found, below which a significant　Vac dependent change occurs in the energy dissipation for the sample at 32 bar. A Vac dependence　of the ”non-classical rotational inertia” fraction(NCRIF) also appears below ∼ T0. This value of T0　excludes the possible explanation of supersolid by liquid superfluidity in grain boundaries or other　liquid related origins. The log(Vac) linear dependence was found in NCRIF. Furthermore, this linear　slope changes in proportion to 1/T2 for 40 < Vac < 400 μm/s, then crosses over to ∼ 1/T for larger　Vac. We discuss properties of the vortex fluid proposed by Anderson above Tc and below T0.

PACS numbers: 67.80.bd, 67.25.dk, 67.25.dt, 67.85.De.