Spin-reorientation-induced band gap in Fe$_3$Sn$_2$: Optical signatures of Weyl nodes

TL;DR

This study uses infrared spectroscopy to explore how spin reorientation in Fe$_3$Sn$_2$ affects its electronic structure, revealing a band gap opening and signatures of Weyl nodes linked to magnetic transitions.

Contribution

It demonstrates the impact of spin reorientation on the electronic band structure and identifies optical signatures of Weyl nodes in Fe$_3$Sn$_2$, a magnetic kagome metal.

Findings

Spectral weight redistribution occurs with spin reorientation.

A sharp mode indicates a band gap opening due to spin reorientation.

Optical signatures suggest the presence of Weyl nodes.

Abstract

Temperature- and frequency-dependent infrared spectroscopy identifies two contributions to the electronic properties of the magnetic kagome metal Fe$_3$Sn$_2$: two-dimensional Dirac fermions and strongly correlated flat bands. The interband transitions within the linearly dispersing Dirac bands appear as a two-step feature along with a very narrow Drude component due to intraband contribution. Low-lying absorption features indicate flat bands with multiple van Hove singularities. Localized charge carriers are seen as a Drude-peak shifted to finite frequencies. The spectral weight is redistributed when the spins are reoriented at low temperatures; a sharp mode appears suggesting the opening of a gap due to the spin reorientation as the sign of additional Weyl nodes in the system.