Thermally activated and quantum plasticity of solid 3He at temperatures below 0.5 K

Plastic flow of solid ³He through a porous membrane frozen in the crystal is observed in the temperature range from 0.1 to 0.5 K. The flow of helium through the pores of the membrane occurs under the mechanical stress caused by the electrostatic force. It was found that the temperature dependence of the flow velocity V has two characteristic regions: at temperatures above T ∼0.2 K, V decreases exponentially with lowering temperature, which corresponds to the thermally activated process, and at temperatures below 0.2 K, V is independent on T , which indicates the quantum mechanism of mass transfer. For the high-temperature region the values of thermal activation volume and energy of activation are estimated. The results are analyzed in the framework of vacancy and dislocation models of plastic flow.