Theory of plastic vortex creep

We develop a theory for plastic vortex creep in a topologically disordered (dislocated) vortex solid phase in type-II superconductors in terms of driv en thermally activated dislocation dynamics. Plastic barriers for dislocati ons show a power-law divergence at small driving currents j, U-pl (j) propo rtional to j(- mu), With mu = 1 for a single dislocation and mu = 2/5 for c reep of dislocation bundles. This implies a suppression of the creep rate a t the transition from the ordered vortex phase (mu = 2/11) to the dislocate d glass and can manifest itself as an observed increase of the apparent cri tical current (second peak). Our approach applies to general dynamics of di sordered elastic media on a random substrate.