Rashba spin-orbit coupling in graphene monolayer coated by periodic magnetic stripes

Xiaojing Li,Zhenhua Wu,Jiangtao Liu

doi:10.1038/s41598-017-06821-9

Abstract

We investigate theoretically the effects of a modulated periodic perpendicular magnetic fields and the Rashba spin-orbit coupling (RSOC) on the electronic states and optical absorption spectrum in a graphene monolayer. The magnetic fields and supperlattice geometry give rise to distinct Dirac cone shift and open a finite bandgap at the Dirac point. In contrast to the energy spectrum without the RSOC interaction, we find that the RSOC term will develop a spin-splitting energy-momentum dispersion relation in this graphene magnetic supperlattice. Anisotropic and spin-split group velocities, effective masses and the momentum-dependent carrier distributions along the magnetic strips are demonstrated. And the manipulations of these exotic properties by tuning the magnetic fields and the RSOC are addressed systematically. Accordingly, we find bright-to-dark transitions in the electron-hole pairs transition rate spectrum and absorption peak splitting in the optical absorption spectrum tuned by the RSOC interaction. This feature offers us a practical way to detect these band engineering effects especially the exotic spin splitting states by using the conductance and optical technique.

Highlights

Graphene monolayer and few layers have been created by mechanical exfoliation of small mesas of graphite, CVD, graphite oxidation reduction and other chemical synthesis methods[1], especially the monolayer graphene has the most impressive two-dimensional electron gas properties, including long phase coherence lengths, strong electric field responses, Dirac fermions behaviors with no energy dissipation, which promise a great potential for the applications in the nano-electronics
The Rashba spin-orbit coupling (RSOC) in graphene arising from crystal with structural inversion asymmetry by impurities or external electric fields has been theoretically predicted[17, 18] and experimentally observed[19]
We propose a magneto-optical instrument utilizing a graphene magnetic superlattice which can be realized by coating a periodic array of ferromagnetic stripes above it. we demonstrate a clear conception about the graphene monolayer under periodic magnetic stripes, which leads to a magnetic superlattice in graphene without the need for cutting or etching

Summary

Introduction

Graphene monolayer and few layers have been created by mechanical exfoliation of small mesas of graphite, CVD, graphite oxidation reduction and other chemical synthesis methods[1], especially the monolayer graphene has the most impressive two-dimensional electron gas properties, including long phase coherence lengths, strong electric field responses, Dirac fermions behaviors with no energy dissipation, which promise a great potential for the applications in the nano-electronics. A great deal of attention has been devoted to superlattice structures, where external spatially periodic electric[7,8,9,10,11,12] and/or magnetic fields are applied to a graphene monolayer[13,14,15,16]. In these previous studies, people have found anisotropic energy dispersion and gap modulation by the external fields. We can find the highly anisotropic behavior in transition rate spectrum and spin splitting states in optical absorption

Methods

Discussion

Conclusion