Strong Pinning and Plastic Deformations of the Vortex Lattice.

We investigate numerically the dynamically generated plastic deformations of a 3D vortex lattice driven through a disorder potential with isolated, strong pinning centers (pointlike or extended along the field direction). We find that the vortex lattice exhibits a very peculiar dynamical behavior in the plastic flow regime, in particular, topological excitations consisting of three or four entangled vortices are formed. We determine the critical current density {ital j}{sub {ital c}} and the activation energy for depinning {ital U}{sub {ital c}} in the presence of a finite density of strong pinning centers. {copyright} {ital 1996 The American Physical Society.}