Encoding orbital angular momentum of light in magnets

TL;DR

This paper explores how optical vortices carrying orbital angular momentum can induce subwavelength magnetic phenomena, including spin wave anisotropy and topological defect generation, with potential applications in magnetic control at nanoscale.

Contribution

It introduces OAM-dependent magnetic phenomena induced by optical vortices, demonstrating new ways to manipulate magnetic states at subwavelength scales.

Findings

Generation of radially anisotropic spin waves.

Creation of topological defects in chiral magnets.

Reduction of skyrmion formation timescales.

Abstract

Breaking the diffraction limit and focusing laser beams to subwavelength scale are becoming possible with the help of recent developments in plasmonics. Such subwavelength focusing bridges different length scales of laser beams and matter. Here we consider optical vortex, or laser beam carrying orbital angular momentum (OAM) and discuss potential subwavelength magnetic phenomena induced by such laser. On the basis of numerical calculations using Landau-Lifshitz-Gilbert equation, we propose two OAM-dependent phenomena induced by optical vortices, generation of radially anisotropic spin waves and generation of topological defects in chiral magnets. The former could lead to the transient topological Hall effect through the laser-induced scalar spin chirality, and the latter reduces the timescale of generating skyrmionic defects by several orders compared to other known means.