Noncollinear magnetic phases and edge states in graphene quantum Hall bars

TL;DR

This paper investigates the magnetic phases and edge states in graphene quantum Hall bars under magnetic fields, revealing how different magnetic orders influence edge states and induce back-scattering, with implications for spintronic applications.

Contribution

It provides an integrated theoretical description of bulk and edge magnetic phases in graphene Hall bars using a non-collinear mean field Hubbard model, highlighting edge state behaviors.

Findings

Edge magnetic orders are either enhanced or suppressed depending on edge type.

Preformed local moments can interact with quantum Spin Hall edge states.

Different magnetic phases lead to distinct edge state properties and back-scattering phenomena.

Abstract

Application of a perpendicular magnetic field to charge neutral graphene is expected to result in a variety of broken symmetry phases, including antiferromagnetic, canted and ferromagnetic. All these phases open a gap in bulk but have very different edge states and non-collinear spin order, recently confirmed experimentally. Here we provide an integrated description of both edge and bulk for the various magnetic phases of graphene Hall bars making use of a non-collinear mean field Hubbard model. Our calculations show that, at the edges, the three types of magnetic order are either enhanced (zigzag) or suppressed (armchair). Interestingly, we find that preformed local moments in zigzag edges interact with the quantum Spin Hall like edge states of the ferromagnetic phase and can induce back-scattering.