High-temperature Quantum Spin Hall Effect And Giant Rashba Spin-orbit Coupling In Compensated N-p Codoped Graphene

Graphene,an intrinsic two-dimensional topological insulator(TI)because of the Dirac nature of its charge carriers and the spin-orbit couplings(SOCs)which are able to manipulate the spin degree of freedom,has been considered as a promising candidate material for spintronic applications.Enhancement of the spin-orbit coupling(SOC)in graphene may lead to various topological phenomena,such as Quantum Spin Hall Effect(QSHE),Quantum Anomalous Hall Effect(QAHE),and also find applications in spintronics.In fact,the QSH effect was first suggested in graphene,it opens an small energy gap at the Dirac point due to the smaller intrinsic SOC of graphene.Therefore,QSHE is not easy to be observed in the experiment.Then the spin-orbit coupling effect was studied again through the experiment and theoretical calculation.For instance,the quantum spin Hall effect(QSH)has been experimentally observed in some quantum wells.However,ultrahigh quality samples and ultralow temperature due to extremely small band gap severely limits its potential application in dissipation-less quantum electronics.Increasing the SOC strength in graphene without drastically affecting the basic physical properties is proving extremely difficult.Using the calculation method of this article is based on first principles,and we systemically studied the following two aspects of content,based on the idea of compensating n–p codoping.(1)We study of the electronic structures of the F4-TCNQ/Tl codoped graphene based on compensated n-p codoping scheme.Our results show that a large and intrinsic band gap,more important,the band gap of Tl/graphene/F4-TCNQ system is almost no effect by building a variety of configurations,and it is tunable by the Tl doping concentration.This study provides a new solution for experimental studies and practical applications of the high-tempertature QSH effect.(2)We study of the electronic and especially spintronic properties of the B/Tl and B/In codoped grapheme based on compensated n-p codoping scheme.We found that it can simultaneously address all the main shortcomings associated with single-element adsorption in graphene,and the charge compensated nature of the n–p codopants helps to preserve the Dirac nature of the charge carriers;effectively resulting in giant Rashba spin-orbit splitting,and its magnitude reaches 130 me V(at 6.25% B/Tl codoped graphene).In addition,the B doping effect together with intrinsic induced SOC by Tl adatom also lead the codoped system open about 20 ~90 me V band gap.This study provides a theoretical basisfor design a new typeof graphene spintronics materical.