Topological spin-transfer drag driven by skyrmion diffusion

TL;DR

This paper demonstrates a topological spin-transfer drag mechanism mediated by skyrmion diffusion in magnetic insulators, showing algebraic decay of voltage signals and potential for characterizing chiral magnetic phases.

Contribution

It introduces a novel topological spin-transfer drag effect driven by skyrmion Brownian motion, contrasting with traditional magnon-based spin drag.

Findings

Voltage signal decays algebraically with contact separation

Topological charge transfer is mediated by skyrmion diffusion

Method can characterize phase diagrams of chiral magnets

Abstract

We study the spin-transfer drag mediated by the Brownian motion of skyrmions. The essential idea is illustrated in a two-terminal geometry, in which a thin film of a magnetic insulator is placed in between two metallic reservoirs. An electric current in one of the terminals pumps topological charge into the magnet via a spin-transfer torque. The charge diffuses over the bulk of the system as stable skyrmion textures. By Onsager's reciprocity, the topological charge leaving the magnet produces an electromotive force in the second terminal. The voltage signal decays algebraically with the separation between contacts, in contrast to the exponential suppression of the spin drag driven by non-protected excitations like magnons. We show how this topological effect can be used as a tool to characterize the phase diagram of chiral magnets and thin films with interfacial Dzyaloshinskii-Moriya interactions.