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

TL;DR

This paper investigates the electronic structure of ferromagnetic kagome metal Fe3Sn2, revealing helical nodal lines and spin-orbit effects that lead to topological phases, providing insights for designing materials with novel quantum properties.

Contribution

It identifies helical nodal lines in Fe3Sn2 and demonstrates how spin-orbit coupling influences their topological nature, offering a new perspective on kagome metals as model Dirac systems.

Findings

Helical nodal lines exist near K and K' points in Fe3Sn2.

Spin-orbit coupling can gap the nodal lines or create Weyl points.

Fe3Sn2 serves as a model Dirac kagome metal with tunable topological phases.

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. 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, 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.