Effect of submicron holes on the vortex dynamcis of a superconducting microbridge

We measured and compared the electric field vs current density characteristics in the vortex state of two amorphous Nb0.7Ge0.3 microbridges, with and without a line of submicron holes patterned along the sample axis. The power dissipation in the perforated sample exhibits a crossover, being reduced at temperatures well below the superconducting transition temperature Tc and unexpectedly enhanced close to Tc. At low temperatures the holes are efficient artificial pinning centers and reduce the average vortex velocity. We argue that the dissipation enhancement close to Tc is a consequence of a combination of the weakened pinning by the holes and an inhomogeneous driving-current distribution in their vicinity, which results in an increased average vortex velocity as well as in a channeling of the vortex motion through the holes.