Plastic flow of solid 3He through a porous elastic film

A study of plastic flow of solid 3He through a metalized porous elastic polymer film frozen into the crystal was carried out in the temperature range of 0.1–1 K. The flow was due to mechanical stresses in the crystal induced by external electrical forces. The plastic flow rate of solid helium was determined by measuring the capacitance changes of a capacitor in which the metalized surface of the film served as a movable electrode. Two different regions could be clearly identified on the temperature dependence of the plastic flow rate V(T). Above ∼200 mK, V drops exponentially with decreasing temperature, which corresponds to the thermally activated regime of plastic flow. At lower temperatures, the rate V is temperature independent, indicating quantum plastic flow. A detailed analysis of the experimental data was performed in the thermally activated region. The empirical values of the following parameters were defined: the activation volume and energy and the yield strength, corresponding to the onset of ...