Ferromagnetic helical nodal line and Kane-Mele spin-orbit coupling in kagome metal Fe3Sn2

Abstract

The two-dimensional kagome lattice hosts Dirac fermions at its Brillouin zone corners K and K , analogous to the honeycomb lattice. In the density functional theory electronic structure of ferromagnetic kagome metal Fe 3 Sn 2 , without spin-orbit coupling, we identify two energetically split helical nodal lines winding along z in the vicinity of K and K resulting from the trigonal stacking of the kagome layers. We find that hopping across A-A stacking introduces a layer splitting in energy while that across A-B stacking controls the momentum space amplitude of the helical nodal lines. We identify the latter to be one order of magnitude weaker than the former owing to the underlying d-orbital degrees of freedom. The effect of spin-orbit coupling is found to resemble that of a Kane-Mele term, where the nodal lines can either be fully gapped to quasi-two-dimensional massive Dirac fermions, or remain gapless at discrete Weyl points depending on the ferromagnetic moment orientation. Aside from numerically establishing Fe 3 Sn 2 as a model Dirac kagome metal by clarifying the roles played by interplane coupling, our results provide insights into materials design of topological phases from the lattice point of view, where paradigmatic low dimensional lattice models often find realizations in crystalline materials with three-dimensional stacking.

Field-dependent Shubnikov-de Haas oscillations in ferromagnetic Weyl semimetal Co3Sn2S2

“…Viewed alternatively from the perspective of kagome lattice metals, we may contrast the 3D Fermi surfaces observed here in Co 3 Sn 2 S 2 with the quasi-two-dimensional Dirac fermiology reported in Fe 3 Sn 2 [11,32] and FeSn [33]. The tunability of the dimensionality of the topological states in magnetic kagome metals may be attributed to the orbital degrees of freedom of the underlying 3d electrons [33][34][35]. With increasing interplane hopping, ferromagnetic kagome metals connect a 3D quantum anomalous Hall insulator phase to a 3D Weyl semimetallic phase, suggesting a topological phase diagram resembling the seminal theoretical proposal of building Weyl semimetallic phases using stacked topological insulating layers [4].…”

High-temperature concomitant metal-insulator and spin-reorientation transitions in a compressed nodal-line ferrimagnet Mn3Si2Te6

“…Topological magnets where the symmetry-protected band degeneracy is coupled with magnetism have emerged as a new material platform for novel transport phenomena and spintronic functionalities 1 – 7 . Among various types of topological magnets, the so-called nodal-line magnetic semimetals or semiconductors are one of the most seminal examples that exhibit unprecedentedly large magnetotransport responses, including giant anomalous Hall effect (AHE) 8 – 14 and colossal angular magnetoresistance (AMR) 15 – 17 . Unlike Dirac or Weyl magnets, the topological nodal-line magnets possess lines or loops of the band degeneracy in the momentum space, which can be lifted effectively by tunable spin-orbit coupling (SOC), producing strong Berry curvature with spin orientation.…”

Electronic structure, optical properties and defect induced half-metallic ferromagnetism in kagome Cs2Ni3S4

“…Mineral jarosite is the first kagome compound which has been experimentally found [3]. The kagome lattice exhibits interesting electronic properties due to its unique geometric arrangement [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The family of ternary transition metal chalcogenides, represented by the formula A 2 M 3 X 4 (where A are K, Rb, Cs; M are Ni, Pd, Pt; and X are S, Se), is commonly found to exhibit various crystal symmetries [20].…”