Flux pinning and current-induced vortex motion at T -> 0 in two-dimensional vortex glass

摘要

We investigate the roles of flux pinning on vortex motion at low temperatures (T) in two-dimensional (2D) superconductors using two thin (4 nm) amorphous MoxSi1-x films with different pinning strength. We measure the T dependence of resistance R at fields B below the critical field B-c of the 2D superconductor-insulator (SI) transition. For both films we observe the very small T-independent R at T --> 0 in certain field regions below B-c, suggesting quantum motion of a small number of vortices (dislocations) in the 2D vortex-glass phase in the presence of current. For the film with weaker pinning, the activation energy decreases at T < 0.1 K. [References: 9]