Ab initio study of spin-dependent transport in carbon nanotubes with iron and vanadium adatoms

TL;DR

This study investigates how iron and vanadium adatoms affect spin-dependent electron transport in carbon nanotubes, revealing spin-specific scattering mechanisms and their dependence on nanotube size using ab initio methods.

Contribution

It introduces a combined ab initio and tight-binding approach to analyze spin-dependent scattering in nanotubes with transition metal adatoms, highlighting the role of d-orbital coupling.

Findings

Adatoms cause spin-specific scattering and Fano resonances.

Scattering depends on the d-state filling of the adatoms.

Transmission dips decrease in width as nanotube size increases.

Abstract

We present an ab initio study of spin dependent transport in armchair carbon nanotubes with transition metal adsorbates, iron or vanadium. We neglect the effect of tube curvature and model the nanotube by graphene with periodic boundary conditions. A density functional theory based nonequilibrium Green's function method is used to compute the electronic structure and zero-bias conductance. The presence of the adsorbate causes a strong scattering of electrons of one spin type only. The scattering is shown to be due to coupling of the two armchair band states to the metal 3d orbitals with matching symmetry causing Fano resonances appearing as dips in the transmission function. The spin type (majority/minority) being scattered depends on the adsorbate and is explained in terms of d-state filling. The results are qualitatively reproduced using a simple tight-binding model, which is then used to investigate the dependence of the transmission on the nanotube width. We find a decrease in the width of the transmission dip as the tube-size increases.