Creep of b-Sn single crystals in a sub-Kelvin temperature range

Abstract

The b-Sn single crystals oriented to creep favourably in the (100) <010> system are studied in a 0.45–4.2 K range. A transient creep is recorded above and below 1 K, the creep being damped with time by the logarithmic law. The temperature dependence of the logarithmic creep coefficient is studied comprehensively. It is found that there are two qualitatively different regions in the curve: in a 4.2–1.2 K range the coefficient decreases linearly with temperature; and below 1 K the creep becomes athermic and the coefficient remains unchanged. The experimental behaviors are shown to fit in with the concepts according to which the creep kinetics of pure b-Sn is determined by the dislocation motion within the potential Peierls relief by the mechanism of nucleating paired kinks in the dislocation lines. The process entails overcoming the effective potential barrier of order of 0.001 eV: at T < 1 K the paired kink nucleation occurs due to the quantum tunneling and the creep is of pure quantum behavior; for higher temperatures the thermal fluctuations are dominant and the creep kinetics corresponds to the classical views of thermally activated creep. Empirical estimates of mobile dislocation density and work-hardening coefficient are obtained.