Topological edge states of a graphene zigzag nanoribbon with spontaneous edge magnetism

TL;DR

This paper explores how spontaneous edge magnetism in graphene zigzag nanoribbons influences their topological edge states, revealing new magnetic configurations and potential for spintronic device engineering.

Contribution

It demonstrates the impact of Hubbard interaction and spontaneous magnetization on the topological phases and edge states of graphene nanoribbons, including the existence of quasi-stable excited states.

Findings

Spontaneous edge magnetism alters topological phases.

Quasi-stable excited states suppress finite size effects.

Magnetic configurations influence edge state properties.

Abstract

The topological phases of graphene with spin-orbit coupling, an exchange field, and a staggered-sublattice potential determine the properties of the edge states of the zigzag nanoribbon. In the presence of the Hubbard interaction, the spontaneous magnetization at the zigzag terminations induces sizable magnetic moments at the lattice sites in the bulk region. Thus, the exchange field and staggered-sublattice potential in the bulk region are effectively changed, which in turn change the topological phase. Within a certain parameter regime, quasi-stable excited states of the zigzag nanoribbon exist, which have a different magnetism configuration at the zigzag terminations from the ground state. The quasi-stable excited states could effectively suppress the finite size effect of the topological edge states. The investigation of the topological edge states in the presence of interaction helps the engineering of spintronic nanodevices based on realistic materials.