Annealing in solid ${}^4$He

Abstract

We have used a torsional oscillator with square cross section and a resonance frequency of 185 Hz to confirm the nonclassical rotational inertia (NCRI) discovered by Kim and Chan\cite{1,2}. We have also found a strong correlation between the NCRI signal and a high dissipation Q${}^{-1}$ of 4 $\times$ 10${}^{-6}$ of the oscillation above the transition temperature. Here, we present preliminary results of the annealing process in ${}^4$He at a pressure of 26 bar. When holding the temperature constant above 1 K we have observed a immediate rise in the period and a slow decay of the dissipation. The equilibrium value of Q${}^{-1}$ decreases with increasing temperature.

6 pages, 4 figures conference proceedings for QFS2007 (to be published in Journal of Low Temperature Physics)