# Temperature-induced band shift in ferromagnetic Weyl semimetal Co3Sn2S2

## TL;DR

This study investigates how temperature affects the electronic band structure of ferromagnetic Weyl semimetal Co3Sn2S2, revealing that magnetization-driven band shifts can be detected via optical spectra, confirming its magnetic Weyl semimetal nature.

## Contribution

It provides the first systematic experimental and theoretical analysis of temperature-dependent optical spectra in Co3Sn2S2, demonstrating tunable Weyl nodes via magnetization changes.

## Key findings

- Band renormalization factor of about 1.33 due to Co 3d electrons.
- Optical spectra detect temperature-induced band shifts and magnetic phase transition.
- Weyl nodes in Co3Sn2S2 can be tuned by temperature-driven magnetization.

## Abstract

The discovery of nonmagnetic Weyl semimetals (WSMs) in TaAs compounds has triggered lots of efforts in finding its magnetic counterpart. While the direct observation of the Weyl nodes and Fermi arcs in a magnetic candidate through angle-resolved photoemission spectroscopy is hindered by the complex magnetic domains. The transport features of magnetic WSMs, including negative magnetoresistivity and anomalous Hall conductivity, are not conclusive since these are sensitive to extrinsic factors like defects and disorders in lattice or magnetic ordering. Here, we systematically study the temperature-dependent optical spectra of ferromagnetic Co$_3$Sn$_2$S$_2$ experimentally and simulated by first-principles calculations. The many-body correlation effect due to Co $3d$ electrons leads to the renormalization of bands by a factor about 1.33, which is moderate and the description within density functional theory is suitable. As the temperature drops down, the magnetic phase transition happens and the magnetization drives the band shift through exchange splitting. The optical spectra can well detect these changes, including the transitions sensitive and insensitive to the magnetization, and those from the bands around the Weyl nodes. The results strongly support that Co$_3$Sn$_2$S$_2$ is a magnetic WSM and the Weyl nodes can be tuned by magnetization with temperature change.