Elementary-flux-pinning potential in type-II superconductors

Flux pinning brought about by quasiparticle scattering off small-spatial-extent defects is studied using the quasiclassical method. The theory as applied to the pinning problem is presented in detail and an efficient method is given for solving the transportlike equation of the theory numerically. The pinning potential of a model impurity with hard-sphere---scattering phase shifts is computed over the entire temperature range in a pure superconductor with the Ginzburg-Landau parameter κ=0.9. The pinning energies arising from quasiparticle scattering turn out to be up to 2 orders of magnitude larger than those predicted by the traditional theory for small-spatial-extent pinning centers.