B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Pr. Nauky, Kharkiv 61103, Ukraine
Received June 3, 2016
A study of plastic flow of solid 3He through a metallized porous elastic polymer film, the frozen-in crystal, is carried out in the temperature range of 0.1–1 K. The flow was caused by mechanical stresses in the crystal, which created by an external electrical power. The velocity of the solid helium plastic flow was determined by measuring changes in capacitance of the measuring capacitor, in which the metallized surface of the film served as a movable electrode. Two areas can be clearly identified on the temperature dependence of the flow velocity V. Above ~ 200 mK the value of V decreases exponentially with decreasing of temperature, which corresponds to the thermally activated regime of plastic flow. At lower temperatures the velocity V does not depend on temperature, indicating a quantum plastic flow. A detailed analysis of experimental data is performed in the thermally activated region. The empirical values of the following parameters are defined: activation volume, the activation energy and the threshold stress above which there is a macroscopic plastic flow. It is found that the value of the activation volume in 30–70 times more than the atomic volume, indicating that the scale of the structural rearrangements in the crystal at the elementary acts of plastic flow is significantly higher than the atomic size. In this case the activation energy is close to the value of the vacancy activation energy. The experimental results are analyzed in the framework of the diffusion-vacancy and dislocation models of plastic flow. In the dislocation model we estimated the temperature below which dislocations overcome barriers Peierls by quantum tunneling. The appendix discusses the physical foundations of the methodology used and the results of the theory of the dislocation motion in the Peierls relief, which were used to analyze the characteristics of the plastic flow of solid 3He.
PACS: 62.20.F– Deformation and plasticity; PACS: 67.80–s Quantum solids; PACS: 67.80D– Solid 3He PACS: 67.80.dj Defects, impurities, and diffusion.