Observation via spin Seebeck effect of macroscopic magnetic transport from emergent magnetic monopoles

Abstract

Magnetic monopoles, elusive in high-energy physics, have been realised as emergent quasiparticles in solid-state systems, where their unique properties hold promise for novel spintronic applications. Magnetic monopoles have been invoked in diverse platforms, including skyrmion lattices, chiral magnets, soft ferromagnets, aritifical nanomagnets. Yet, a demonstration of their role in magnetic transport has remained elusive. Here, we report such an observation via the spin Seebeck effect in the bulk insulating pyrochlore oxide, spin ice $\mathrm{D}{\mathrm{y}}_2\mathrm{T}{\mathrm{i}}_2{\mathrm{O}}_7$. By applying a thermal gradient perpendicular to a $[111]$-oriented magnetic field, we detect a transverse spin Seebeck voltage marked by a dominant peak at the onset of monopole proliferation, accompanied by a secondary feature and frequency-dependent behavior. Our findings establish a direct link between monopole dynamics and magnetic transport in an insulating medium, establishing a new pathway for probing fractionalized excitations and advancing towards novel spintronic applications.

This submission has been superseded by a new version arXiv:2606.02501, which includes major revisions and an expanded author list