Disorder-based graphene spintronics

TL;DR

This paper demonstrates that disorder in doped graphene nanoribbons can be harnessed to achieve perfect spin filtering, with 100% spin polarization arising from different localization lengths for each spin channel, using ab initio calculations.

Contribution

It introduces a novel mechanism where disorder enhances spin filtering in graphene nanoribbons, enabling perfect spin polarization.

Findings

Disorder can induce 100% spin polarization in graphene nanoribbons.

Different localization lengths for spins explain the spin filtering effect.

The effect is enhanced by the exponential dependence of conductance on device length.

Abstract

The use of the spin of the electron as the ultimate logic bit - in what has been dubbed spintronics - can lead to a novel way of thinking about information flow. At the same time single layer graphene has been the subject of intense research due to both its fundamental properties as well as its potential application in nanoscale electronics. While defects can significantly alter the electronic properties of nanoscopic systems, the lack of control can lead to seemingly deleterious effects arising from the random arrangement of such impurities. Here we demonstrate, using {\it ab initio} density functional theory and non-equilibrium Green's functions calculations, that it is possible to obtain perfect spin selectivity in doped graphene nanoribbons to produce a perfect spin filter. We show that initially unpolarized electrons entering the system give rise to 100% polarization of the current due to random disorder. This effect is explained in terms of different localization lengths for each spin channel which together with the well know exponential dependence of the conductance on the length of the device leads to a new mechanism for the spin filtering effect that is enhanced by disorder.