Spin currents in rough graphene nanoribbons: Universal fluctuations and spin injection

TL;DR

This paper studies spin conductance in graphene nanoribbons, revealing how edge structure influences spin injection capabilities and uncovering universal conductance fluctuations in rough nanoribbons.

Contribution

It introduces a spin injection mechanism based on nanostructure edge asymmetry and characterizes universal conductance fluctuations in rough nanoribbons.

Findings

Straight edges yield zero spin conductance.

Asymmetric edges enable finite spin conductance.

Rough edges cause universal conductance fluctuations of about 0.4 e/4π.

Abstract

We investigate spin conductance in zigzag graphene nanoribbons and propose a spin injection mechanism based only on graphitic nanostructures. We find that nanoribbons with atomically straight, symmetric edges show zero spin conductance, but nonzero spin Hall conductance. Only nanoribbons with asymmetrically shaped edges give rise to a finite spin conductance and can be used for spin injection into graphene. Furthermore, nanoribbons with rough edges exhibit mesoscopic spin conductance fluctuations with a universal value of $\mathrm{rms} G_\mathrm{s}\approx 0.4 e/4\pi$.