Dynamic Regimes in Films with a Periodic Array of Antidots

TL;DR

This study investigates the dynamic behavior of Pb thin films with a periodic antidot array, revealing how vortex motion and pinning regimes change with ac drive amplitude, temperature, and magnetic field, and confirming Bean model scaling.

Contribution

It provides new insights into vortex dynamics and pinning regimes in antidot-patterned superconducting films, highlighting the transition from low to high amplitude responses and the associated pinning strength changes.

Findings

Vortices exhibit a frequency- and amplitude-independent response at low drive amplitudes.

A critical state develops when vortex displacement exceeds pinning range at higher amplitudes.

Scaling laws based on the Bean model are validated in the critical state regime.

Abstract

We have studied the dynamic response of Pb thin films with a square array of antidots by means of ac susceptibility chi(T,H) measurements. At low enough ac drive amplitudes h, vortices moving inside the pinning potential give rise to a frequency- and h-independent response together with a scarce dissipation. For higher amplitudes, the average distance travelled by vortices surpasses the pinning range and a critical state develops. We found that the boundary h*(H,T) between these regimes smoothly decreases as T increases whereas a step-like behavior is observed as a function of field. We demonstrate that these steps in h*(H) arise from sharp changes in the pinning strength corresponding to different vortex configurations. For a wide set of data at several fields and temperatures in the critical state regime, we show that the scaling laws based on the simple Bean model are satisfied.