Spin-orbit locking of magnons with localized microwave fields

TL;DR

This paper explores how microwave-induced spin-orbit coupling in magnetic systems enables directional magnon excitation and tunable coupling between nanomagnets, revealing new ways to control magnonic interactions.

Contribution

It demonstrates the realization of spin-orbit locking of magnons using localized microwave fields, introducing a novel mechanism for directional magnon excitation and tunable nanomagnet coupling.

Findings

Microwave spin-orbit locking causes directional magnon beams.

Magnon exchange enables tunable strong coupling between nanomagnets.

Directional control of magnons is achieved via fixed chirality and evanescent fields.

Abstract

We address the photonic spin-orbit coupling known from nano-optics and plasmonics in the microwave regime. The spin $\mathbf{S}$ and momentum $\mathbf{q}$ of microwaves emitted by an excited magnetic particle are locked by $\mathbf{q}\cdot\mathbf{S}=0$ with a fixed chirality $\hat{\mathbf{n}}\cdot(\hat{\bf S}\times\hat{\bf q})=1$ when evanescent along $\hat{\mathbf{n}}\perp {\bf q}$. This field excites magnons in a nearby magnetic film in the form of directional beams that rotate with the magnetization direction. The exchange of these magnons between two distant nanomagnets leads to a highly tunable strong coupling and entangles their excited states.