Signatures for half-metallicity and nontrivial surface states in a Kagome-lattice magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$

TL;DR

This study uses scanning tunneling microscopy to investigate the surface states and band structure of the magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$, revealing a spin-minority gap and signatures of nontrivial surface states.

Contribution

It provides direct experimental evidence of the bulk and surface electronic structures of Co$_3$Sn$_2$S$_2$, highlighting surface signatures of nontrivial states in a magnetic Weyl semimetal.

Findings

Identification of surface terminations and local density of states.

Observation of a ~300 mV semimetal gap in spin-minority bands.

Detection of nontrivial surface states around 50 mV.

Abstract

Weyl semimetals with time reversal symmetry breaking are expected to show various fascinating physical behaviors, such as intrinsic giant anomalous Hall effect, chiral anomaly effect in the bulks, and Fermi arcs on the surfaces. Here we report a scanning tunneling microscopy study on the magnetic Weyl semimetal candidate Co$_3$Sn$_2$S$_2$. According to the morphology and local density of states of the surface, we provide assignments to different surface terminations. The measured local density of states reveals a semimetal gap of ~300 mV, which is further verified as the gap in spin-minority bands using spin-resolved tunneling spectra. Additionally, signature for the nontrivial surface states around 50 mV is proposed. This is further confirmed by the observations of standing waves around a step-edge of the sample. Our observations and their comparison with band structure calculations provide direct yet timely evidence for the bulk and surface band structures of the magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$.