Correlation length of quasiperiodic vortex lattices.

We investigated vortex-lattice dynamics in superconducting Nb thin films with different quasiperiodic arrays of magnetic pinning centers. The mixed-state magnetoresistance exhibits minima for well-defined applied fields, related to matching effects between the vortex lattice and those arrays. The results show that critical matching can originate at a local scale. For fractal arrays, the vortex-lattice correlation length is longer and the minima are deeper, close to those of periodic arrays.