Non-local exchange effects in zigzag edge magnetism of neutral graphene nanoribbons

TL;DR

This paper investigates how non-local exchange interactions influence the magnetic properties of zigzag graphene nanoribbons, revealing enhanced edge magnetism and band-gap effects beyond local interaction models.

Contribution

It demonstrates that non-local exchange stabilizes magnetic features and increases band-gaps in zigzag graphene nanoribbons, surpassing local exchange approximations.

Findings

Non-local exchange stabilizes magnetic features.

Inter-edge exchange enhances the band-gap.

Local models cannot replicate the effects of non-local exchange.

Abstract

We study the role of non-locality of exchange in a neutral zigzag graphene nanoribbon within the $\pi$-orbital unrestricted Hartree-Fock approximation. Within this theory we find that the magnetic features are further stabilized for both the intra-edge and inter-edge exchange compared to mean field theories of zigzag ribbon based on local exchange (like the Hubbard model or the ab-initio Local Density Approximation). The inter-edge exchange produces an enhancement of the band-gap of the magnetic ground-state solutions. The effect of this enhanced exchange on the edge states can not be satisfactorily achieved by a local interaction with renormalized parameters.