Spin-transfer torque generated in graphene based topological insulator heterostructures

Qingtian Zhang,Jingbo Li,K S Chan

doi:10.1038/s41598-018-22680-4

Abstract

We studied the spin-transfer torque (STT) in graphene based normal-metal/topological-insulator/ferromagnet heterostructures (N/TI/F), which is induced by the helical spin-polarized current in the quantum spin Hall insulator. We found that the STT is comparable in magnitude to the STT in ferromagnetic-normal- ferromagnetic graphene junction, while not requiring additional ferromagnetic layer with fixed magnetization, which makes it advantageous for the manipulation of magnetic devices in spintronics. More interestingly, the STT is very robust in our proposed nanostructure, as it is immune to changes in the geometry due to an asymmetrically notch or the presence of random nanopores in the quantum spin Hall insulator. Our theoretical prediction suggests that graphene based quantum spin Hall insulator could be used for very efficient magnetization manipulation for magnetic materials.

Highlights

The topological insulator is a new quantum state of matter characterized by an insulating bulk gap and gapless edge states topologically protected, which has been intensively studied owing to the new physical properties and potential technological applications[1,2,3,4,5,6,7,8,9,10,11]
Spin-transfer torque (STT) is an important spintronic phenomenon, in which a spin current injected into a ferromagnetic layer exerts a torque on the magnetic layer and may change its magnetization orientation[26]
Motivated by the successful idea of realizing quantum spin Hall insulator in graphene and the recent measurements of the STT induced by a topological insulator[30], we theoretically study the generation of the STT in graphene nanoribbon through a quantum spin Hall insulator

Summary

Introduction

The topological insulator is a new quantum state of matter characterized by an insulating bulk gap and gapless edge states topologically protected, which has been intensively studied owing to the new physical properties and potential technological applications[1,2,3,4,5,6,7,8,9,10,11]. When spin current flows into a ferromagnetic layer, the magnetization of the ferromagnetic layer exerts a torque on the electron spins and the spin current exerts an equal but opposite torque on the ferromagnetic layer, so the orientation of magnetization is modified[27] This spintronic effect was predicted independently by Slonczewski[28] and Berger[29], and it has been confirmed in many experiments[30,31,32,33,34,35,36]. Motivated by the successful idea of realizing quantum spin Hall insulator in graphene and the recent measurements of the STT induced by a topological insulator[30], we theoretically study the generation of the STT in graphene nanoribbon through a quantum spin Hall insulator. Graphene based N/TI/F heterostructures, and the STT can not be affected by asymmetrically notched the ribbon or nanopores

Methods

Results

Conclusion