Adatoms in graphene as a source of current polarization: Role of the local magnetic moment

TL;DR

This paper theoretically explores how adatoms in graphene can generate spin-polarized currents, emphasizing the importance of localized levels near the Fermi energy and demonstrating gate control as a means to tune spin polarization.

Contribution

It identifies the key role of spin-split localized levels near the Fermi energy in achieving current polarization, and shows how gate potentials can control spin-polarized currents in graphene with adatoms.

Findings

Local magnetic moments are necessary but not sufficient for current polarization.

Spin-split localized levels near the Fermi energy enable polarization.

Gate potentials can tune the localized levels and control spin polarization.

Abstract

We theoretically investigate spin-resolved currents flowing in large-area graphene, with and without defects, doped with single atoms of noble metals (Cu, Ag and Au) and 3d-transition metals (Mn,Fe,Co and Ni). We show that the presence of a local magnetic moment is a necessary but not sufficient condition to have a non zero current polarization. An essential requirement is the presence of spin-split localized levels near the Fermi energy that strongly hybridize with the graphene pi-bands. We also show that a gate potential can be used to tune the energy of these localized levels, leading to an external way to control the degree of spin-polarized current without the application of a magnetic field.