摘要
层状Kagome金属由于包含平带和线性交叉的狄拉克(Dirac)带等奇异电子性质,正逐渐成为探索阻挫晶格和量子拓扑的新兴电子材料.该文采用第一性原理方法研究了应变和Hubbard相互作用U对CoSn和CoGe两种层状Kagome金属拓扑电子性质的调控.研究结果表明,对两种Kagome金属施加a和b单轴应变时,能够较大地减少六边形Co原子d轨道的局域化程度,导致Kagome金属中平带宽度发生较大的改变,并且单轴应变破坏了晶体的C6对称性,从而使得Dirac点发生劈裂,且劈裂程度随应变的增加而增加.而c轴应变对Co原子d轨道的局域化程度影响较小,因而平带宽度变化较小.当施加ab双轴应变时,平带宽度变化没有单轴应变明显,表明对称性对保持Kagome晶格中六边形金属原子的d轨道消相干效发挥了重要作用.并且由于双轴应变没有破缺晶体对称性,Dirac点在拉伸应变下只发生移动,而在压缩应变下由于自旋劈裂导致四重简并Dirac点劈裂为两个二重简并的外尔(Weyl)点,形成平带-Weyl带的新型能带结构.研究还表明,较大的库仑相互作用(Hubbard-U)对Kagome电子结构同样存在重要影响.当U> 1.60 eV时,不仅能带发生了自旋劈裂,而且平带宽度和Dirac点位置发生了明显的改变,Hubbard-U对Kagome晶格中局域化的Co原子d轨道产生了重要的影响.这些发现为进一步深入探讨Kagome金属的拓扑电子性质和关联效应提供了研究思路,也为其在能源、催化等领域中的实际应用提供了理论参考.
Layered Kagome metals,due to the electronic properties such as flat bands and linearly crossing Dirac bands,are gradually becoming novel emerging electronic materials for exploring frustrated lattices and quantum topologies.In this paper,the first-principles method is used to study the regulation of strain and Hubbard interaction U on the topological and electronic properties of two layered Kagome metals,CoSn and CoGe.The results show that applying a-axis and b-axis strain to CoSn and CoGe Kagome metals can significantly reduce the degree of localization of the d orbitals of hexagonal Co atoms,leading to significant changes in the width of flat bands in the Kagome metal.And uniaxial strain destroys the C 6 symmetry of the crystal,resulting in the occurrence of splitting at the Dirac point,and the degree of splitting increases with the increase of strain.However,the c-axis strain has a small impact on the localization degree of the d orbitals of the Co atom,resulting in a small variation in the width of the flat bands.When ab biaxial strain is applied,the width of flat band changes less significantly than uniaxial strain,indicating that the crystal symmetry plays an important role in maintaining the d orbital decoherence effect of hexagonal metal atoms in the Kagome lattice.Moreover,the biaxial strain does not break the crystal symmetry,and the Dirac point only moves under tensile strain,while under compressive strain,a four-fold degenerate Dirac point splits into two two-fold degenerate Weyl points due to spin splitting,forming a novel energy band structure of flat band-Weyl band.The study also shows that the larger Hubbard-U interaction has an important effect on the Kagome electronic structure.When U>1.60 eV,not only the energy bands undergo spin splitting,but also the width of the flat band and the position of the Dirac points have significantly changed.Hubbard-U has an important influence on the localized d orbitals of Co atoms in the Kagome lattice.These findings provide insights of further studies of the to
作者
彭虽然
李意芝
孟利军
PENG Suiran;LI Yizhi;MENG Lijun(School of Physics and Optoelectronics,Xiangtan University,Xiangtan 411105,China)
出处
《湘潭大学学报（自然科学版）》
CAS
2024年第4期60-68,共9页
Journal of Xiangtan University(Natural Science Edition)
基金
国家自然科学基金(11204261)
湖南省自然科学基金(2018JJ2381)
湖南省教育厅重点项目(19A471)。
