Dynamics of flux penetration and critical currents in type-II superconductors

Abstract

We study the dynamics of flux penetration and vortex pinning in a type-II superconductor by numerical simulations with forces appropriate in the London regime. Straight vortex lines at zero temperature are studied in a slab geometry, and, unlike previous studies, full account is taken of the dynamical penetration of the flux lines across the surface under the application of an external magnetic field. Our simulation produces flux penetration in the sample beyond ${H}_{c1}$ as expected, with the flux lines forming an Abrikosov lattice in the absence of the pinning centers. The pinning centers impede flux penetration into the bulk and the resulting critical current decreases with increasing vortex density roughly in agreement with the modified Bean's model.