First Principles Calculations of Spin-Dependent Conductance of Graphene Flakes

TL;DR

This study employs first principles calculations to analyze the spin-dependent conductance in hydrogen-terminated graphene flakes, revealing their potential for spintronic applications through edge state manipulation and magnetic adatom functionalization.

Contribution

It demonstrates that pure and functionalized graphene flakes can generate spin-polarized currents using edge states and magnetic adatoms, advancing understanding of spin transport in graphene nanostructures.

Findings

Hydrogen-terminated graphene flakes are structurally stable with properties similar to nanoribbons.

Pure graphene flakes can produce spin-polarized currents via asymmetric contacts.

Vanadium functionalization induces spin polarization even with symmetric contacts.

Abstract

Using ab initio density functional theory and quantum transport calculations based on nonequilibrium Green's function formalism we study structural, electronic, and transport properties of hydrogen-terminated short graphene nanoribbons (graphene flakes) and their functionalization with vanadium atoms. Rectangular graphene flakes are stable, having geometric and electronic structures quite similar to that of extended graphene nanoribbons. We show that a spin-polarized current can be produced by pure, hydrogenated rectangular graphene flakes by exploiting the spatially-separated edge states of the flake using asymmetric, non-magnetic contacts. Functionalization of the graphene flake with magnetic adatoms such as vanadium also leads to spin-polarized currents even with symmetric contacts. We observe and discuss sharp discontinuities in the transmission spectra which arise from Fano resonances of localized states in the flake.