Influence of nonuniform critical current density profile on magnetic field behavior of AC susceptibility in 2D Josephson junction arrays

Employing mutual-inductance measurements, we study the magnetic field dependence of complex AC susceptibility of artificially prepared highly ordered (periodic) two-dimensional Josephson junction arrays of unshunted Nb–AlOx–Nb junctions. The observed behavior can be explained assuming single-plaquette approximation of the overdamped model with an inhomogeneous critical current distribution within a single junction.