New Dissipation Relaxation Phenomenon in Oscillating Solid He-4
  We describe the first observations on the time-dependent dissipation when the drive level of a torsional oscillator containing solid He-4 is abruptly changed. The relaxation of dissipation in solid He-4 shows rich dynamical behavior including exponential and logarithmic time-dependent decays, hysteresis, and memory effects. 
Y. Aoki, M. C. Keiderling, and H. Kojima