Anisotropic avalanches and flux penetration in patterned superconductors

Both for a fundamental understanding of the flux penetration process and for technical applications, the role of artificial pinning sites (such as antidots) in superconductors generates a lot of interest. We perform magneto-optical imaging experiments on type-II Pb thin films patterned with square arrays of square antidots and square arrays of rectangular antidots and blind holes. We demonstrate that a square lattice of rectangular antidots can lead to similar anisotropy in flux penetration and critical current as a rectangular lattice of square antidots. In addition we show how thermo-magnetic avalanches can be guided—and hence to a certain extend controlled—by such holes.