Ultrafast magnetic flux dendrite propagation into thin superconducting films

We suggest a theoretical model allowing one to find analytically the velocity of a magnetic flux dendrite penetration into thin superconducting films. The key assumptions for this model are based upon experimental observations. We treat a dendrite tip motion as a propagating flux jump instability. Two different regimes of dendrite propagation are found: A fast initial stage is followed by a slow stage, which sets in as soon as a dendrite enters into the vortex-free region. The theoretical results and experimental data obtained by a magneto-optic pump-probe technique are compared and a good agreement between the calculations and measurements is found.