Tunable edge magnetism at graphene/graphane interfaces

TL;DR

This paper investigates how electrostatic gating can control edge magnetism at graphene/graphane interfaces, revealing a quantum phase transition to a ferromagnetic state that could help distinguish magnetic effects from disorder in graphene nanoribbons.

Contribution

It introduces a theoretical framework combining mean-field and bosonization techniques to demonstrate tunable edge magnetism and a quantum phase transition in graphene/graphane interfaces.

Findings

Edge magnetism can be switched on and off by electrostatic gates.

A quantum phase transition between ordinary and ferromagnetic Luttinger liquids is identified.

The mechanism offers a way to distinguish edge magnetism from disorder in graphene nanoribbons.

Abstract

We study the magnetic properties of graphene edges and graphene/graphane interfaces under the influence of electrostatic gates. For this, an effective low-energy theory for the edge states, which is derived from the Hubbard model of the honeycomb lattice, is used. We first study the edge state model in a mean-field approximation for the Hubbard Hamiltonian and show that it reproduces the results of the extended 2D lattice theory. Quantum fluctuations around the mean-field theory of the effective one-dimensional model are treated by means of the bosonization technique in order to check the stability of the mean-field solution. We find that edge magnetism at graphene/graphane interfaces can be switched on and off by means of electrostatic gates. We describe a quantum phase transition between an ordinary and a ferromagnetic Luttinger liquid - a realization of itinerant one-dimensional ferromagnetism. This mechanism may provide means to experimentally discriminate between edge magnetism or disorder as the reason for a transport gap in very clean graphene nanoribbons.