Switchable crossed spin conductance in a graphene-based junction: The role of spin-orbit coupling

Hossein Hamzehpour,Razieh Beiranvand

doi:10.1038/s41598-020-58799-6

Hossein Hamzehpour, Razieh Beiranvand

Open Access

https://doi.org/10.1038/s41598-020-58799-6

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Journal: Scientific Reports	Publication Date: Feb 6, 2020
Citations: 2	License type: open-access

Affiliation: K.N.Toosi University of Technology

Abstract

We theoretically investigate the crossed spin conductance (CSC) of a graphene-based heterostructure consists of ferromagnet, Rashba spin-orbit and superconductor regions. Using Dirac Bogoliubov-de Gennes formalism in the ballistic regime, we show that in the presence of Rashba spin-orbit coupling there are an anomalous crossed Andreev reection and spin-ipped co-tunneling in the process of quantum transport. We demonstrate that the CSC can be reversed with respect to charge conductance by tuning the Rashba spin-orbit coupling which experimentally can be adjusted by the applied perpendicular electric field on the graphene sheet. This feature in addition to a long spin relaxation time of Dirac fermions in graphene proposes designing a device with a non-local spin switch which is crucial for spintronics circuits.

Highlights

We theoretically investigate the crossed spin conductance (CSC) of a graphene-based heterostructure consists of ferromagnet, Rashba spin-orbit and superconductor regions
The last one which is known as Rashba spin-orbit (RSO) interaction[30], arises from a perpendicular electric field or interactions with substrate[31]
We show that the sign of the spin conductance can be switch from positive to negative by changing RSO interaction which is experimentally possible by tuning perpendicular electric field

Summary

Introduction

We theoretically investigate the crossed spin conductance (CSC) of a graphene-based heterostructure consists of ferromagnet, Rashba spin-orbit and superconductor regions. We demonstrate that the CSC can be reversed with respect to charge conductance by tuning the Rashba spin-orbit coupling which experimentally can be adjusted by the applied perpendicular electric field on the graphene sheet. This feature in addition to a long spin relaxation time of Dirac fermions in graphene proposes designing a device with a non-local spin switch which is crucial for spintronics circuits. The incident quasi-particle at the interface of one lead can be reflected as a quasi-hole in the other lead, giving rise to a negative non local conductance This so-called crossed Andreev reflection (CAR) competes with elastic co-tunneling (CT). Using gate voltage and tuning Fermi level, the sign of charge conductance in the ferromagnetic drain lead (F2) can be negative

Methods

Conclusion