Band engineering aided by topological edge state proximity effects: Inducing anti-chirality in graphene

TL;DR

This paper investigates how non-uniform magnetic fields in graphene nanoribbons induce topological domain walls, leading to band structure modifications and the emergence of anti-chiral edge states with co-propagating currents.

Contribution

It introduces a novel mechanism for band engineering in graphene via topological edge state proximity effects, demonstrating anti-chirality emergence.

Findings

Proximity between edge states modifies the band structure near domain walls.

Anti-chirality arises with co-propagating edge currents and bulk states.

Magnetic field variation enhances edge state coupling.

Abstract

In this work we analyze infinite graphene nanoribbons subjected to non-uniform magnetic fields that produce topological domain walls in the quantum Hall regime. We show how the proximity between edge states from neighboring domains modifies the band structure due to the state coupling near the domain walls. The proximity-induced band deformations produce phenomena such as bulk-like dispersion that coexist with Landau levels and valley-polarized current paths. It is shown that edge state coupling can be enhanced by continuously varying the magnetic field between two non-trivial topological phases. The mechanism by which neighboring edge states modify the band structure is addressed by tracking their wave-functions over isolated bands and by analyzing the magnetic confinement potential near the domain wall. By calculating the local current density, we show that the coexistence of topological edge states with bulk-like dispersion can lead to the appearance of anti-chirality, in which co-propagating currents appear in the edges while the rest of the nanoribbon is occupied with bulk states. The appearance of anti-chirality is justified by comparing the proposed non-uniform magnetic field profile with an anti-chiral modified Haldane model.