Origin of the matching effect in a superconducting film with a hole array

We investigate the origin of the matching effect observed in superconducting Nb films containing regular arrays of holes near the zero-field critical temperature. We find “dips” in the resistance vs magnetic field curves at matching fields where the magnitude of the magnetic flux threading each unit cell is an integer number of the flux quantum. By comparing the magnetic field dependences of the resistance and critical temperature in perpendicular and parallel magnetic field directions, we find that the matching effect in Nb films containing triangular hole arrays originates from hole-induced suppression of the critical temperature rather than the widely assumed flux pinning enhancement.