Dynamic Aspects of Strong Pinning

We determine the current--voltage characteristic of type II superconductors in the presence of strong pinning centers. Focusing on a small density of defects, we derive a generic form for the characteristic with a linear flux-flow branch shifted by the critical current (excess-current characteristic). The details near onset, a hysteretic jump (for $\kappa \gg 1$) or a smooth velocity turn-on ($\kappa \to 1$), depend on the Labusch parameter $\kappa$ characterising the pinning centers. Pushing the single-pin analysis into the weak pinning domain, we reproduce the collective pinning results for the critical current.