Limited robustness of edge magnetism in zigzag graphene nanoribbons with electrodes

TL;DR

This paper investigates how external contacts and geometric factors weaken edge magnetism in zigzag graphene nanoribbons, showing that increased transparency and certain aspect ratios diminish magnetic moments.

Contribution

It introduces a theoretical analysis demonstrating the destructive impact of electrode coupling and aspect ratio on edge magnetism in graphene nanoribbons.

Findings

Edge magnetism decreases with more transparent graphene/electrode interfaces.

Aspect ratio significantly influences the suppression of edge magnetism.

External contacts are detrimental to magnetic moment formation.

Abstract

It is shown that apart from well-known factors, like temperature, substrate, and edge reconstruction effects, also the presence of external contacts is destructive for the formation of magnetic moments at the edges of graphene nanoribbons. The edge magnetism gradually decreases when graphene/electrode interfaces become more and more transparent for electrons. In addition to the graphene/electrode coupling strength, also the aspect ratio parameter, i.e. a width/length ratio of the graphene nanoribbon, is crucial for the suppression of edge magnetism. The present theory uses a tight-binding method, based on the mean-field Hubbard Hamiltonian for $\pi$ electrons, and the Green's function technique within the Landauer-B\"uttiker approach.