# Inhomogeneity in electronic phase and flat band in magnetic kagome metal Co3Sn2S2

## TL;DR

The study investigates the magnetic and electronic properties of Co3Sn2S2, revealing inhomogeneous electronic phases and a flat band at the Fermi level.

## Contribution

The discovery of a flat band at the Fermi level and electronic inhomogeneity in Co3Sn2S2 adds new insights into its complex electronic structure.

## Key findings

- X-ray Magnetic Circular Dichroism shows Co magnetic moments come from spin, not orbital.
- Spatially-resolved photoemission reveals a butterfly-shaped band structure in some regions.
- A sharp flat band at the Fermi level is detected and attributed to a surface state.

## Abstract

Co3Sn2S2 has been reported to be a Weyl semimetal with c-axis ferromagnetism below a Curie temperature of 177 K. Despite the large interest in Co3Sn2S2, the magnetic structure is still unclear. Recent studies have challenged the magnetic phase diagram of Co3Sn2S2 by reporting unusual magnetic phases including the presence of exchange bias. Here we show, using X-ray Magnetic Circular Dichroism, a shift in the magnetization hysteresis loop, reminiscent of exchange bias and establish that the magnetic moment in Co arises from the spin, with negligible orbital moment. At 6 K, using spatially-resolved angle-resolved photoemission spectroscopy, we detect a butterfly-shaped electronic band structure at small regions of the sample distinct from the known ferromagnetic band structure. Our density functional theory calculations suggest that the butterfly bands correspond to an antiferromagnetic phase. Separately, we detect a sharp flat band at the Fermi level at some regions in the sample, which we attribute to a surface state. These different electronic states found in a stoichiometric intermetallic invite further efforts to explore the origin and nature of the electronic inhomogeneity associated to magnetism on the mesoscale.

Co₃Sn₂S₂ has been reported to be a Weyl semimetal but its magnetic and electronic structure is still under debate. Here, X-ray magnetic circular dichroism reveals that cobalt magnetic moments originate from spin, rather than orbital moments, whereas spatially-resolved angle-resolved photoemission spectroscopy indicates the presence of electronic inhomogeneities in the band structure and magnetic phases.