The Ic(H)-Tc(H) phase boundary of superconducting Nb thin films with periodic and quasiperiodic antidot arrays

The magnetic field dependent critical current Ic(H) of superconducting thin films with artificial defects strongly depends on the symmetry of the defect arrangement. Likewise the critical temperature Tc(H) of superconducting wire networks is heavily influenced by the symmetry of the system. Here we present experimental data on the Ic(H)-Tc(H) phase boundary of Nb thin films with artificial defect lattices of different symmetries. For this purpose we fabricated 60 nm thick Nb films with antidots in periodic (triangular) and five different quasiperiodic arrangements. The parameters of the antidot arrays were varied to investigate the influence of antidot diameter and array density. Experiments were performed with high temperature stability (ΔT<1 mK) at 0.5≤T/Tc≤1. From the I-V-characteristics at variable H and T we extract Ic(H) and Tc(H) for different voltage and resistance criteria. The experimental data for the critical current density are compared with results from numerical molecular dynamics simulations.