Collective vortex rectification effects in films with a periodic pinning array

TL;DR

This study investigates vortex rectification in patterned aluminum films, revealing how asymmetry and collective vortex dynamics influence voltage rectification under various driving conditions.

Contribution

It demonstrates the distinct mechanisms of rectification in asymmetric and symmetric antidots and uncovers collective vortex behaviors affecting the ratchet effect.

Findings

Rectification in asymmetric antidots is due to intrinsic pinning potential asymmetry.

Rectification in symmetric antidots is driven by an applied dc bias.

Collective vortex phenomena cause multiple rectification peaks below the first matching field.

Abstract

The vortex ratchet effect has been studied in Al films patterned with square arrays of submicron antidots. We have investigated the transport properties of two sets of samples: (i) asymmetrical antidots where vortices are driven by an unbiased ac current, and (ii) symmetrical antidots where in addition to the ac drive a dc bias was used. For each sample, the rectified (dc) voltage is measured as a function of drive amplitude and frequency, magnetic field, and temperature. As unambiguously shown by our data, the voltage rectification in the asymmetric antidots is induced by the intrinsic asymmetry in the pinning potential created by the antidots, whereas the rectification in the symmetric antidots is induced by the dc bias. In addition, the experiments reveal interesting collective phenomena in the vortex ratchet effect. At fields below the first matching field ($H_1$), the dc voltage--ac drive characteristics present two rectification peaks, which is interpreted as an interplay between the one-dimensional motion of weakly pinned incommensurate vortex rows and the two-dimensional motion of the whole vortex lattice. We also discuss the different dynamical regimes controlling the motion of interstitial and trapped vortices at fields slightly higher than $H_1$ and their implications for the vortex ratchet effect.