AC-susceptibility of superconducting films with a periodic pinning array

Abstract

We use AC-susceptibility measurements to study the dynamic response of vortices in a Pb thin film with a periodic array of antidots. In the linear regime, from the field dependence of the AC-penetration depth λ we determine the curvature of the pinning potential well α for different matching fields. For applied fields H below the first matching field H 1, α reaches its highest value due to the strong vortex localization at the pinning sites. For H 1< H< H 2, the metallic-like behavior of interstitial vortices gives rise to a reduction of α and a further decrease of the pinning strength is observed for H 2< H< H 3. However, for H 3< H< H 4, a reentrance in the pinning strength appears, due to a specific configuration of the flux line lattice which strongly restricts the mobility of vortices.