Statistics of the vortex pinning potential in superconducting films

Abstract

We investigate the statistical properties of the vortex pinning potential in a thin superconducting film. Modeling intrinsic inhomogeneities by a random-temperature Ginzburg-Landau functional with short-range Gaussian disorder, we derive the pinning landscape $E(\mathbf{R})$ by determining how the vortex core adapts to randomness. Within the hard-core approximation, applicable for weak disorder, the energy landscape exhibits Gaussian statistics. In this regime, the mean areal density of its minima is given by $n_\text{min}\approx(6\xi)^{-2}$, indicating that the typical spacing between neighboring minima is significantly larger than the vortex core size $\xi$. Going beyond the hard-core approximation, we allow the vortex order parameter to relax in response to the inhomogeneities. As a result, the pinning potential statistics become non-Gaussian. We calculate the leading correction due to the core deformation, which reduces the density of minima with a relative magnitude scaling as $(T_c-T)^{-1/2}$.