Origin of matching effect in anti-dot array of superconducting NbN thin films

Abstract

We investigate the origin of the matching effect observed in disordered superconducting NbN thin films with a periodic array of holes. In addition to the periodic variation in electrical resistance just above the superconducting transition temperature T_c0, we find pronounced periodic variations with magnetic field in all dynamical quantities that can be influenced by flux-line motion under an external drive, including the magnetic shielding response and the critical current, which survives in some samples down to temperatures as low as 0.09T_c0. In contrast, the superconducting energy gap Δ, which is a true thermodynamic quantity, does not show any periodic variation with magnetic field for the same films. Our results show that commensurate pinning of the flux-line lattice driven by vortex–vortex interaction is the dominant mechanism for the matching effects observed in these superconducting anti-dot films, rather than a Little–Parks-like quantum interference effect.