Flux Pinning and Current-Induced Vortex Motion at T→0 in Two-Dimensional Vortex Glass

Abstract

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 Mo x Si 1-x films with different pinning strength. We measure the T dependence of resistance R at fields B below the critical field Bc 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 Bc, 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 .