Hysteresis magnetoresistance and edge superconductivity in Nb film with diluted square array of holes

Abstract

We investigated the transport properties of a superconducting Nb film with a diluted square array of holes, in which one fourth of the sites were removed from the original square lattice. The edge-to-edge separation of the holes in the sample is comparable to the superconducting coherence length, resulting in a system similar to multi-connected superconducting islands. Three regions in magnetoresistance (R(H)) curves can be identified. In the low field region, fluxoid quantization leads to fine structures in R(H) and T c (H) curves. At higher fields, the entering and leaving of interstitial vortices results in a novel field and temperature dependent hysteresis. At even higher fields, weak oscillations in resistance were observed due to edge superconductivity of inter-hole biconcave thin necks and Little-Parks effect. Moreover, the edge state results in a remarkable field induced narrowing of superconducting transition width.