Shape induced anomalies in vortex pinning and dynamics of superconducting antidot arrays with spherical cavities

Abstract

Using electrochemical deposition of Pb in the pores of templates prepared by self-assembly from colloidal suspensions of polystyrene latex spheres, well ordered superconducting antidot arrays with spherically shaped holes are fabricated. In contrast to conventional lithographic arrays the samples with spherical cavities demonstrate significantly reduced pinning strength favoring the formation of commensurate states. The ac-flux penetration acquires a hybrid intra- and intervalley regime. For high ac drives an unusual inversion to paramagnetic ac shielding is found at commensurate states.