Controllable spin-dependent transport in armchair graphene nanoribbon structures

TL;DR

This paper investigates how ferromagnetic gating can control spin-dependent transport in armchair graphene nanoribbons, revealing high spin polarization and the influence of contact nature and band gap on conductance.

Contribution

It introduces a detailed analysis of spin transport in GNRs using NEGF formalism, highlighting the effects of width, contacts, and gate voltage on spin polarization.

Findings

High spin polarization close to 100% in certain junctions.

Oscillatory conductance and spin polarization with gate voltage.

Confined states significantly affect transport properties.

Abstract

Using the non-equilibrium Green's functions formalism in a tight binding model, the spin-dependent transport in armchair graphene nanoribbon (GNR) structures controlled by a ferromagnetic gate is investigated. Beyond the oscillatory behavior of conductance and spin polarization with respect to the barrier height, which can be tuned by the gate voltage, we especially analyze the effect of width-dependent band gap and the nature of contacts. The oscillation of spin polarization in the GNRs with a large band gap is strong in comparison with 2D-graphene structures. Very high spin polarization (close to 100%) is observed in normal-conductor/graphene/normal-conductor junctions. Moreover, we find that the difference of electronic structure between normal conductor and graphene generates confined states in the device which have a strong influence on the transport quantities. It suggests that the device should be carefully designed to obtain high controllability of spin current.