Highly Effective Superconducting Vortex Pinning in Conformal Crystals

We have investigated the vortex dynamics in superconducting thin film devices with non-uniform patterns of artificial pinning centers (APCs). The magneto-transport properties of a conformal crystal and a randomly diluted APC pattern are compared with that of a triangular reference lattice. We have found that in both cases the magneto-resistance below the first matching field of the triangular reference lattice is significantly reduced. For the conformal crystal, the magneto-resistance is below the noise floor indicating highly effective vortex pinning over a wide magnetic field range. Further, we have discovered that for asymmetric patterns the R vs. H curves are mostly symmetric.This implies that the enhanced vortex pinning is due to the commensurability with a stripe in the non-uniform APC pattern and not due to a rearrangement and compression of the whole vortex lattice.
Comment: submitted to APL on 29/04/13