Magnetic adatoms in two and four terminal graphene nanoribbons: A comparison between their spin polarized transport

TL;DR

This paper investigates charge and spin transport in graphene nanoribbons with magnetic adatoms, revealing how spin components and conductance behaviors change with Rashba spin-orbit interaction and adatom density, impacting spintronic device design.

Contribution

It provides a comparative analysis of two- and four-terminal GNRs with magnetic adatoms, highlighting the effects of Rashba SOI on spin conductance components and phase transitions.

Findings

Magnetic adatoms induce only z-component spin conductance without Rashba SOI.

Presence of Rashba SOI enables all three spin components in conductance.

Magnetic adatoms transform quantum spin Hall phase into an insulator.

Abstract

We study the charge and spin transport in two and four terminal graphene nanoribbons (GNR) decorated with random distribution of magnetic adatoms. The inclusion of the magnetic adatoms generates only the $z$-component of the spin polarized conductance via an exchange bias in the absence of Rashba spin-orbit interaction (SOI), while in presence of Rashba SOI, one is able to create all the three ($x$, $y$ and $z$) components. This has important consequences for possible spintronic applications. The charge conductance shows interesting behaviour near the zero of the Fermi energy. Where in presence of magnetic adatoms the familiar plateau at $2e^2/h$ vanishes, thereby transforming a quantum spin Hall insulating phase to an ordinary insulator. The local charge current and the local spin current provide an intuitive idea on the conductance features of the system. We found that, the local charge current is independent of Rashba SOI, while the three components of the local spin currents are sensitive to Rashba SOI. Moreover the fluctuations of the spin polarized conductance are found to be useful quantities as they show specific trends, that is, they enhance with increasing adatom densities. A two terminal GNR device seems to be better suited for possible spintronic applications.