本征磁性拓扑绝缘体MnBi2Te4电子结构的压力应变调控

由于MnBi2Te4电子结构具有对晶格常数的改变相当敏感的特性,本文采用基于密度泛函理论的第一性原理方法对MnBi2Te4反铁磁块体的电子结构施加等体积应变调控.研究发现体系能带结构在材料等体积拉伸和压缩作用下变化灵敏,体系出现绝缘体-金属相变.特别地,当施加特定应变后导带和价带在Γ处出现交叉,体系呈零带隙状态.在此应变下仍可观察到能带反转的现象,具有非平庸的能带拓扑性质.根据不同应变下的电荷密度图,发现等体积应变会影响体系七倍层层间距,其中等体积压缩和拉伸应变可分别增大和减小Te原子层间距,表明等体积压缩有利于降低反铁磁层间耦合.通过等体积压力应变调控,掌握了MnBi2Te4的电子结构的变化规律,这对本征磁性拓扑绝缘体MnBi2Te4的物性研究和实验制备具有重要的指导意义.

Pressure strain control of electronic structure of intrinsic magnetic topological insulator MnBi2Te4

MnBi2Te4 as an intrinsic magnetic topological insulator has attracted lots of attention.Since the electronic structure of MnBi2Te4 is quite sensitive to the change of lattice constant,here in this work,we use a firstprinciples method based on density functional theory to implement the isometric strain control of the electronic structure of MnBi2Te4 antiferromagnetic bulk.The so-called isometric strain is to change the lattice constant under the premise that the volume of the crystal remains unchanged.Our results show that the energy band structure of the system changes sensitively under the action of isometric tension and compression strains of the material,and the system has an insulator-metal phase transition.In particular,when a certain strain is applied,the conduction band and the valence band cross at Γ,and the system presents a zero band gap state.Under this strain,the band inversion can still be observed,showing non-trivial energy band topological properties.According to the charge density and local charge density maps under different strains,it is found that the isometric strain will affect the interlayer spacing of the system’s seven-fold layers.The isometric compression and tensile strain can increase and reduce the Te atomic layer spacing respectively,indicating that isometric compression is beneficial to reducing the antiferromagnetic interlayer coupling.Through the control of isometric pressure and strain,we can master the change law of the electronic structure of MnBi2 Te4,which has important guiding significance for the research of physical properties and experimental preparation of the intrinsic magnetic topological insulator MnBi2Te4.