High-temperature Quantum Anomalous Hall Effect In N-p Codoped Two-dimensional Materials

Quantum Hall effect(QHE)is a fundamental quantum transport phenomenon in condensed physics.In this effect,the strong external magnetic field can produce Landau levels.The underlying mechanisms is the formation of an insulating bulk due to the electron localization in the bulk and conducting edge due to the electron in the edge.The chiral transport property in the edge states is robust against impurity scattering and thus it is promising candidate for low-power electronics application.However,a major constraint for practical use of QHE is the requirement of strong magnetic fields,which is impractical for promising applications.The quantization of Hall effect without external magnetic field,named anomalous quantum Hall effect(QAHE).In 2013,for the first time,Chinese scientists successfully observed this phenomenon in the experiment at extremely low temperatures,which limits its potential applications in the field of electronics in low energy consumption.Hence,high-temperature observation,especially realization of QAHE in some simple material very important.Since graphene and silicene were found,they have become ideal materials of spintronics.Their lattice structure with hexagonal honeycomb structure as the same as that by described Haldane in 1988.Many theoretical and experimental studies have confirmed that the spin orbit coupling effect could be lead to many topological phenomenons,such as quantum spin Hall effect.Previous study has showed that adsorption transition metal on graphene and silicene can significantly enhance extrinsic spin-orbit coupling effect,and open a nontrivial band gap,Then it is possible to realize the high temperature QAHE.However,the adsorption of transition metal(TM)on the graphene usually results in some problems such as adsorption stability,etc.This paper,using the first-principles calculation method,and n-p codoping includes the following contents: 1.We firstly studied the adsorpting of the single 5d TM adatom on the graphene,then studied of the electronic structure of the boron(B)and 5d TM codoped graphene system,The obtained show that the boron(B)/hafnium(Hf)doped graphene system can open a nontrivial gap of ?1 of about 20.5 meV.More importantly,by calculating the boron(B)/rhenium(Re)and boron(B)/platinum(Pt)doped graphene systems,we found that spin splitting phenomenon appears and spin splitting magnitude is about 158 me V,which is several orders of magnitude larger than the repotered graphene's intrinsic SOC.Hence,it is promising to design a new type of spintronic devices.This study provides a new solution for experimental studies and practical applications of the high-temperature QAHE.2.We studied the electronic structure and properties of 5d TM doped silicene material system.We first found that Os doped silicene material system may realize QAHE.In detail,it can open a nontrivial gap of ?1 of about 13.5 me V.At the same time,we calculate the band of the Os doped silicene system under-3% to 2% strains.We found this system may realize anomalous quantum Hall effect,and the band gap of the system is tunable by strain.Thus,this study provides a new scheme for experimental studies and practical applications of the high-tempertature QAHE.