Topological Transport of Vorticity in Heisenberg Magnets

TL;DR

This paper investigates topological vortex transport in a thin ferromagnetic insulator, demonstrating robust vorticity-based spin transport and its potential for nonlocal electrical detection, with implications for topological spintronics.

Contribution

It introduces a novel topological transport mechanism using vortices in 2D magnets, highlighting their robustness and nonlocal electrical signatures, extending topological hydrodynamics to arbitrary dimensions.

Findings

Vortices can be pumped into the insulator by electric currents.

Vortex flow produces measurable electromotive forces at contacts.

Voltage decay follows an algebraic pattern similar to superfluid spin transport.

Abstract

We study a robust topological transport carried by vortices in a thin film of an easy-plane ferromagnetic insulator between two metal contacts. A vortex, which is a nonlocal topological spin texture in two-dimensional magnets, exhibits some beneficial features as compared to skyrmions, which are local topological defects. In particular, the total topological charge carried by vorticity is robust against local fluctuations of the spin order-parameter magnitude. We show that an electric current in one of the magnetized metal contacts can pump vortices into the insulating bulk. Diffusion and nonlocal Coulomb-like interaction between these vortices will establish a steady-state vortex flow. Vortices leaving the bulk produce an electromotive force at another contact, which is related to the current-induced vorticity pumping by the Onsager reciprocity. The voltage signal decays algebraically with the separation between two contacts, similarly to a superfluid spin transport. Finally, the vorticity and closely related skyrmion type topological hydrodynamics are generalized to arbitrary dimensions, in terms of nonsingular order-parameter vector fields.