Spin Conductance of Diffusive Graphene Nanoribbons: a Probe of Zigzag Edge Magnetization

TL;DR

This paper explores how edge magnetization in diffusive zigzag graphene nanoribbons influences spin transport, revealing that external fields can induce finite spin conductance despite an average zero value.

Contribution

It demonstrates that local magnetic moments at zigzag edges cause sample fluctuations in spin currents and shows how external fields can generate finite spin conductance.

Findings

Random edge magnetization causes sample-to-sample spin current fluctuations.

An in-plane electric field can induce finite spin conductance.

External magnetic fields can align edge moments to control spin transport.

Abstract

We investigate spin transport in diffusive graphene nanoribbons with both clean and rough zigzag edges, and long-range potential fluctuations. The long-range fields along the ribbon edges cause the local doping to come close to the charge neutrality point forming $p$-$n$ junctions with localized magnetic moments, similar to the predicted magnetic edge of clean zigzag graphene nanoribbons. The resulting random edge magnetization polarizes charge currents and causes sample-to-sample fluctuations of the spin currents obeying universal predictions. We show furthermore that, although the average spin conductance vanishes, an applied transverse in-plane electric field can generate a finite spin conductance. A similar effect can also be achieved by aligning the edge magnetic moments through an external magnetic field.