Dislocation Motion in hcpHe4

Abstract
Low-frequency measurements of the shear modulus and internal friction of pure and He3-doped crystals of hcp He4 are reported. Previously unobserved features are seen in both quantities. With use of the parameters obtained from our measurements, it is shown for the first time that all the existing dissipation measurements spanning five decades in frequency are consistent with each other and the Granato-Lücke model of overdamped dislocation motion.