Thickness and hole-shape dependence of flux penetration into square superconducting networks

We have observed flux penetrations into square superconducting networks of Nb with various thicknesses and hole-shapes by using magneto-optical imaging method. The penetrated pattern does not depend on the thickness and extends along diagonal direction when the samples have smaller area in the intersection of networks. We have also observed similar superconducting networks with and without small holes at the intersection. The small holes at the intersection do not work as a promoter for the diagonal flux penetration though the parallel flux penetration becomes weak. We discuss possible origins of these anomalous anisotropic flux penetrations.

► In square lattice superconducting networks, flux penetration patterns do not depend on the thickness of superconductors. ► The diagonal penetration of vortices becomes stronger when the hole has sharper edges. ► Small holes at the intersection of networks change the parallel flux penetration to the round shape though the diagonal flux penetration pattern is robust for that pinning or guide.