Electronic and magnetic properties of H-terminated graphene nanoribbons deposited on the topological insulator Sb2Te3.

Wei Zhang,Yan Li,Farideh Hajiheidari,Riccardo Mazzarello

doi:10.1038/srep29009

Abstract

Magnetism in zigzag graphene nanoribbons (GNRs) has received enormous attention recently, due to the one-dimensional nature of this phenomenon, as well as its potential applications in the field of spintronics. In this work, we present a density functional theory (DFT) investigation of H-passivated GNRs on the (111) surface of the topological insulator Sb2Te3. We show that the chemical interaction between the GNR and the substrate is weak. As a result, the GNR-surface distance is large, of the order of 3.4 Angstrom, doping effects are almost negligible, and the mean-field magnetic properties of the GNR are preserved. Nevertheless, the presence of the substrate affects significantly the magnitude of the exchange coupling constants between the edges. Although our DFT calculations do not properly describe quantum fluctuations that destabilize the edge magnetism in free-standing GNRs, they provide important information about the stabilizing mechanisms which originate from the substrate-induced spin orbit coupling and the decoherence effects due to the surface states of Sb2Te3. We argue that, owing to these mechanisms, Sb2Te3 may be a suitable substrate to investigate experimentally the transition from “quantum” to “classical” magnetism in GNRs.

Highlights

Magnetism in zigzag graphene nanoribbons (GNRs) has received enormous attention recently, due to the one-dimensional nature of this phenomenon, as well as its potential applications in the field of spintronics
We focus on the (111) surface of Sb2Te3 and we assume that the GNR is parallel to the (112) direction of the substrate
The bending of the GNR is small and the distance between the GNR and the substrate is around 3.4 Å, which is compatible with the previous study on perfect graphene[27]

Summary

Introduction

Magnetism in zigzag graphene nanoribbons (GNRs) has received enormous attention recently, due to the one-dimensional nature of this phenomenon, as well as its potential applications in the field of spintronics. Our DFT calculations do not properly describe quantum fluctuations that destabilize the edge magnetism in free-standing GNRs, they provide important information about the stabilizing mechanisms which originate from the substrateinduced spin orbit coupling and the decoherence effects due to the surface states of Sb2Te3. A more subtle stabilizing mechanism could occur in the presence of a substrate which possesses surface states near the Fermi energy Such states could lead to decoherence effects and to the emergence of “classical” edge magnetism from the highly entangled singlet ground state[11]. TIs have several remarkable properties, which stem from time-reversal symmetry and strong SOC They possess robust, conducting surface states in the bulk band gap, which exhibit spin-momentum locking and are symmetry protected against non-magnetic disorder

Methods

Results

Conclusion