Shapiro steps in a superconducting film with an antidot lattice

TL;DR

This paper reports the observation of Shapiro voltage steps in a superconducting film with a periodic antidot lattice, demonstrating the phase-coherent motion of interstitial vortices under radiofrequency radiation.

Contribution

It provides experimental evidence of phase-locked interstitial vortex motion in superconducting films with regular pinning arrays, revealing new insights into vortex dynamics.

Findings

Shapiro steps observed at the second matching field H_2

Interstitial vortices are mobile and phase-locked with rf radiation

Pinned vortices remain immobile at antidots

Abstract

Shapiro voltage steps at voltages V_n=nV_0 (n integer) have been observed in the voltage-current characteristics of a superconducting film with a square lattice of perforating microholes (antidots)in the presence of radiofrequent radiation. These equidistant steps appear at the second matching field H_2 when the flow of the interstitial vortex lattice in the periodic potential created by the antidots and the vortices trapped by them, is in phase with the applied rf frequency. Therefore, the observation of Shapiro steps clearly reveals the presence of mobile intersitial vortices in superconducting films with regular pinning arrays. The interstitial vortices, moved by the driving current, coexist with immobile vortices strongly pinned at the antidots.