层状磁性拓扑绝缘体VBi_(2)Te_(4)的第一性原理研究  

A First-Principles Study on Magnetic Topological Insulator of VBi_(2)Te_(4)

作　　者：张会生 王颖颖 杨文佳 张晶晶 许小红[1,2] Zhang Huisheng;Wang Yingying;Yang Wenjia;Zhang Jingjing;Xu Xiaohong(Research Institute of Materials Science,Shanxi Normal Universitty,Linfen 041004,China;Key Laboratory of Magnetic Molecules and Magnetic Information Materials of the Ministry of Education,Shanxi Normal Universitty,Linfen 041004,China;College of Physics and Electronic Information,Shanxi Normal Universitty,Linfen 041004,China)

机构地区：[1]山西师范大学材料科学研究院,山西临汾041004 [2]山西师范大学磁性分子与磁信息材料教育部重点实验室,山西临汾041004 [3]山西师范大学物理与信息工程学院,山西临汾041004

出　　处：《稀有金属》2021年第9期1077-1085,共9页Chinese Journal of Rare Metals

基　　金：国家重点研发计划项目(2017YFB0405703);国家自然科学基金项目(11804210,51871137,61434002);山西省应用基础研究计划项目(201901D211406)资助。

摘　　要：层状磁性拓扑绝缘体MnBi_(2)Te_(4)的发现为探索新颖的量子现象(例如,量子反常霍尔效应和轴子绝缘态等)提供了新的契机。本文利用第一性原理软件VASP系统研究了与MnBi_(2)Te_(4)具有相同构型的新型磁性材料VBi_(2)Te_(4)的磁学、电学以及拓扑特性。研究结果发现VBi_(2)Te_(4)可以稳定存在,并且该材料可以很容易剥离至单层。计算结果表明块体VBi_(2)Te_(4)的层间耦合为反铁磁排列,当不考虑自旋轨道耦合作用时,该体系具有约为0.7 eV的能隙;而考虑自旋轨道耦合作用后,体系的能隙变为0.12 eV且伴随有能带的翻转。进一步的拓扑不变量(Z_(2))和边界态计算表明反铁磁VBi_(2)Te_(4)是三维磁性拓扑绝缘体。对于块体铁磁的VBi_(2)Te_(4),当不考虑自旋轨道耦合作用时,体系的能隙约为0.66 eV;同样地,自旋轨道耦合作用可以引起能带的翻转。随后的边界态计算证明铁磁的VBi_(2)Te_(4)也具有拓扑特性。该研究工作表明,与层状磁性拓扑绝缘体MnBi_(2)Te_(4)一样,磁性VBi_(2)Te_(4)块体材料也具有拓扑特性,其有望来实现各种有趣的拓扑量子态。The recently discovered magnetic topological insulator(TI) of MnBi_(2)Te_(4) had provided unprecedented opportunities to explore emerging quantum phenomena,such as quantum anomalous Hall effect(QAHE) and axion insulating state.Different from randomly doping magnetic atoms in TIs,bulk MnBi_(2)Te_(4) could be seen as that the antiferromagnetic(AFM) MnTe was intercalated into the threedimensional(3D) TI of Bi_(2)Te_(3),where the intralayer Mn atoms in a septuple layer(SL)(e.g.,Te-Bi-Te-Mn-Te-Bi-Te) were magnetically ordered and hosted the long range ferromagnetic(FM) order.Latest theoretical and experimental results had shown that bulk MnBi_(2)Te_(4) was a 3DTI,and the interlayer coupling of two nearest SLs MnBi_(2)Te_(4) was AFM.Such intriguing magnetic properties thus resulted in two distinct quantum phenomena,where odd SLs of MnBi_(2)Te_(4) hosted QAHE,while even SLs of MnBi_(2)Te_(4) exhibited axion insulator state.In particular,the observed temperatures of QAHE in layered MnBi_(2)Te_(4) could be significantly enhanced up to 45 K under an external magnetic field.Most recently,the magnetic material of MnSb_(2)Te_(4) had been experimentally fabricated,and it was found that FM and ferrimagnetic states could be achieved due to the site mixing of Mn and Sb atoms.Moreover,it was predicted that magnetic MnSb_(2)Te_(4) hosted topologically nontrivial states.Therefore,the search for more magnetic materials that hosted intriguingly magnetic topological properties was of great scientific and experimental interest.Here,the structural,electronic and magnetic properties of VBi_(2)Te_(4) were investigated by using the projector augmented wave(PAW) formalism in the Vienna ab initio simulation package(VASP).The Perdew-Burke-Ernzerhof(PBE) approximation was used to describe the exchange and correlation functional.And GGA+U method was employed to better describe the 3d electrons of V atoms in the system,in which the moderate on-site Coulomb interaction(U) and exchange interaction(J) were,respectively,set to 4.0 eV and 1.0 eV.The p

关 键 词：磁性拓扑绝缘体 第一性原理计算 电子结构 拓扑不变量 边界态 

分 类 号：O469[理学—凝聚态物理]