多狄拉克锥的二维CrPSe3的半金属铁磁性与电子结构  

Half-metallic magnetism and electronic structures of CrPSe3 monolayers with multiple Dirac cones

作　　者：杨俊涛 熊永臣 黄海铭 罗时军 Yang Jun-Tao;Xiong Yong-Chen;Huang Hai-Ming;Luo Shi-Jun(School of Science,Hubei University of Automotive Technology,Shiyan 442002,China)

机构地区：[1]湖北汽车工业学院理学院,十堰442002

出　　处：《物理学报》2020年第24期244-252,共9页Acta Physica Sinica

基　　金：湖北省自然科学基金(批准号:2018CFB724,2019CFB788);湖北省教育厅科学研究项目(批准号:D20171803);湖北汽车工业学院学科创新团队项目;国家自然科学基金(批准号:11674113)资助的课题.

摘　　要：采用第一性原理方法和紧束缚模型研究了二维层状结构过渡金属硫族磷化物CrPSe3的磁学特性和电子结构.二维CrPSe3晶格呈现六角蜂窝状结构,声子谱证明其具备较好的动力学稳定性.二维CrPSe3的电子结构呈现出自旋无能隙磁性半金属特性.蒙特卡罗方法模拟出二维CrPSe3的居里温度为224 K,分子动力学表明其具有良好的热力学稳定性.晶体和电子结构研究揭示二维CrPSe3的磁性来源于反铁磁性的d-d直接交换作用和铁磁性的p-d超交换作用间的相互竞争.二维CrPSe3的自旋向上的能带展现出奇异特性:除了高对称点K处出现的一类狄拉克锥之外,在高对称路径Γ-K的中点附近也出现了一类狄拉克锥结构,二者均有较高的费米速度.电子结构表明狄拉克电子主要源于Crdxz和dyz轨道的贡献.在电子结构分析的基础上,采用紧束缚模型对二维CrPSe3费米能级附近的能带进行模拟,结果证明二维CrPSe3的多狄拉克锥结构受过渡金属Cr的六角几何排列对称性保护.该研究为揭示二维材料的磁性机理和研制高温高速自旋器件提供了一良好的模型平台.According to the first-principles calculation within PBE+U method and tight-binding model,the magnetic properties and electronic structures of two-dimensional(2D)CrPSe3 monolayer were investigated.Constructed by a Cr-honeycomb hexagonal lattice,2D CrPSe3 was predicted to be in a half-metallic ferromagnetic state with dynamic stability,confirmed by the phonon spectrum with no imaginary dispersion.The Curie temperature was estimated as 224 K by Monte Carlo simulation within the Metropolis algorithm under the periodic boundary condition.The thermal stability of CrPSe3 monolayer was estimated at 300 K by a first-principles molecular dynamics simulation.It is found that the magnetic ground state of CrPSe3 monolayer is determined by a competition between the antiferomagnetic d-d direct exchange interactions and the Se-p orbitals mediated ferromagnetic p-d superexchange interactions.Most interestingly,in the half-metallic state the band structure exhibits multiple Dirac cones in the first Brillouin zone:two cones at K point showing a very high Fermi velocityυF(K)=15.8×10^5m·s^-1 about twice larger than the of graphene in the vicinity of Fermi level,and six cones at K′/2 points withυF(K′/2)=10.1×10^5m·s^-1 close to the graphene's value.These spin-polarized Dirac cones are mostly composed of Cr dxz and dyz orbitals.The novel electronic structure of CrPSe3 monolayer is also confirmed by the HSE06 functional.A tight-binding model was built based on the Crhoneycomb structure with two Cr-d orbitals as the basic with the first,second and third nearest-neighboring interactions,further demonstrating that the multiple Dirac cones are protected by the Cr-honeycomb lattice symmetry.Our findings indicate that 2D CrPSe3 monolayer is a candidate with potential applications in the low-dimensional,high speed and temperature spintronics.

关 键 词：二维铁磁材料 狄拉克锥 第一性原理 紧束缚近似 

分 类 号：TB34[一般工业技术—材料科学与工程]