The regulation study of strain and Hubbard-U on topological electronic properties in Kagome metals CoSn and CoGe
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 signifi-cantly reduce the degree of localization of the d orbitals of hexagonal Co atoms,leading to significant chan-ges in the width of flat bands in the Kagome metal.And uniaxial strain destroys the C6 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 or-bitals 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 in-to 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 al-so 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 topological electronic properties and correlation effects of Kagome metals,as well as theoretical references for practical applications in energy,catalysis,and other fields.
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