具有大磁晶各向异性能的单层BaPb的室温量子反常霍尔效应  

Room-temperature quantum anomalous Hall effect in monolayer BaPb with large magnetocrystalline anisotropy energies

作　　者：张蔚曦[1] 李勇[1] 田昌海[1] 佘彦超[1] Zhang Wei-Xi;Li Yong;Tian Chang-Hai;She Yan-Chao(Department of Physics and Electronic Engineering,Tongren University,Tongren 554300,China)

机构地区：[1]铜仁学院物理与电子工程系,铜仁554300

出　　处：《物理学报》2021年第15期266-272,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:12064038);贵州省科研项目(批准号:KY[2019]179,KY[2017]315,ZK[2021]一般-034);贵州省优秀青年科技人才项目(批准号:[2019]5673);铜仁市科技局科学技术基金(批准号[2020]77)资助的课题.

摘　　要：具有巨大应用潜力的二维材料在纳米技术领域引起了人们极大的研究兴趣.基于第一性原理计算,本文预测了二维六角晶格BaPb体系具有室温量子反常霍尔效应.体系磁基态是铁磁半金属态,并且自旋极化的Pb-p轨道导致体系的时间反演对称性破缺.具有非零Chern数(C=1)的单层BaPb中非平庸拓扑性来源于全自旋极化的p_(x,y)轨道形成的二次型非狄拉克能带.不同于之前报道的pz轨道形成的狄拉克拓扑态很容易被衬底破坏,p_(x,y)轨道形成的σ键非常稳定.当考虑自旋-轨道耦合作用时,二次型的非狄拉克点打开了接近177.39 meV的非平庸带隙.通过反常霍尔电导、陈数、贝里曲率和边缘态的计算,证实了BaPb非平庸的拓扑性.此外,体系还表现出每个单元52.01 meV的大磁晶各向异性能.The quantum anomalous Hall effect is an intriguing quantum state that exhibits chiral edge states in the absence of a magnetic field.The chiral edge states are topologically protected and robust against electron scattering,which possesses great potential applications in designing low energy consumption and dissipation less spintronic devices.The experimental conditions are required to be very high,such as extremely low temperature(<100 mK) due to the small band gap and the greatly accurate control of the extrinsic impurities.These greatly hinder their devices from being put into applications further.Hence,it would be meaningful to search for a new Chern insulator with a large band gap and high Curie temperature.According to the first-principles calculations,we predict the room temperature quantum anomalous Hall effect in the monolayer BaPb.The nontrivial topology of this new type of ferroelectric semi-metal material derives from fully spin-polarized quadratic non-Dirac bands.The quantum anomalous Hall effect can be realized in the monolayer BaPb with fully spin-polarized quadratic px,y non-Dirac bands with the nonzero Chern number(C=1).Because of the trigonal symmetry of monolayer BaPb material,these bands composed of px,y orbitals are at the Γ point,which is different from the Dirac state formed by the pz orbital reported previously.In addition,it can still retain its original topological properties even if strongly hybridized with the substrate.The calculated phonon spectrum shows no imaginary frequency in the entire Brillouin zone,indicating that the monolayer BaPb system is dynamically stable.By using Monte Carlo simulation,we determine the Curie temperature of BaPb monolayer toreach up to 378 K.We also calculate the magnetic anisotropy energy of the BaPb cell,defined asΔE=E100-E001.Here,we consider two magnetization easy-axis directions,[100] and [001].To our surprise,the MAE of monolayer BaPb is as high as 52.01 meV/cell by considering the spin-orbit coupling effect.Furthermore,the nontrivial band gap is

关 键 词：量子反常霍尔效应 二次型非狄拉克能带 铁磁半金属态 第一性原理 

分 类 号：O469[理学—凝聚态物理]