Tunable ratchet effects for vortices pinned by periodic magnetic dipole arrays

TL;DR

This paper theoretically demonstrates a tunable ratchet effect for vortices in superconducting films interacting with a periodic magnetic dipole array, showing how vortex drift can be controlled by dipole orientation and magnetic fields.

Contribution

It introduces a model for vortex ratchet effects influenced by magnetic dipole arrays and explores how vortex motion can be tuned via dipole orientation and external magnetic fields.

Findings

Vortex drift direction can differ from the driving force direction.

Vortex drift velocity depends on magnetic dipole orientation.

Ratchet effect can be tuned by rotating magnetic dipoles or applying magnetic fields.

Abstract

The ratchet effect is demonstrated theoretically for the simple model of a vortex in a thin superconducting film interacting with a periodic array of magnetic dipoles placed in the vicinity of the film . The pinning potential for the vortex is calculated in the London limit and found to break spatial inversion symmetry and to depend on the orientation of the magnetic dipole moments. The motion of the vortex at zero temperature driven by a force oscillating periodically in time is investigated numerically. Drift vortex motion consisting of displacements by a translation vector of the dipole array during each period of oscillation is obtained and studied in detail. The direction of drift differs in general from that of the driving force, except if the driving force oscillates in a direction of high symmetry of the dipole array. The vortex drift velocity depends on the orientation of the magnetic moments, and can be tuned by rotating the dipoles. It is pointed out that if the magnetic moments are free to rotate, the ratchet effect can be produced and tuned by a magnetic field applied parallel to the film surfaces