Coherent flux flow in superconducting films with periodically modulated thickness

Abstract

We find an anomalous behaviour of the flux flow characteristics of superconducting films with modulated thickness when the vortex lattice matches the periodic pinning structure. At a matching field there is a voltage rise associated with a decrease in supercurrent which is usually not observed for random pinning. Coherent motion of the vortex lattice is responsible for this behaviour. Structure in the differential flux flow resistivity as a function of current can be related to harmonic components of the periodic pinning potential. A recent theory by Schmid and Hauger may be extended to give a satisfactory description of our experiments.