Switchable Weyl nodes in topological Kagome ferromagnet Fe3Sn2

TL;DR

This paper demonstrates that in the ferromagnetic Kagome material Fe3Sn2, Weyl nodes at the Fermi level can be manipulated by changing the magnetization direction, enabling control over topological properties at room temperature.

Contribution

It introduces a method to control Weyl nodes in Fe3Sn2 through magnetization direction, supported by density functional calculations and experimental validation.

Findings

Weyl nodes can be moved in momentum space by magnetization orientation.

Magnetization direction influences the spin polarization texture.

Weyl degeneracies are lifted depending on magnetic orientation.

Abstract

The control of topological quantum materials is the prerequisite for novel devices exploiting these materials. Here we propose that the room temperature ferromagnet Fe3Sn2, whose fundamental building blocks are Kagome bilayers of iron, hosts Weyl nodes at the Fermi level which can move in momentum space depending on the direction of the magnetization, itself readily controlled either by modest external fields or temperature. The proposal is derived from density functional calculations, including a mean field treatment of Hubbard repulsion U, which have been validated by comparison with angle-resolved photoemission data. Ferromagnetism with magnetization along certain directions is shown to lift the Weyl degeneracies, while at the same time inducing texture in the quasiparticle spin polarizations mapped in reciprocal space. In particular, the polarization is attenuated and then rotated from parallel to perpendicular to antiparallel to the magnetization as Weyl points derived from crossing of majority and minority spin bands are traversed.