Unusual Exchange Couplings and Intermediate Temperature Weyl State in Co3Sn2S2

Understanding magnetism and its possible correlations to topological properties has emerged to the forefront as a difficult topic in studying magnetic Weyl semimetals. Co3Sn2S2 is a newly discovered magnetic Weyl semimetal with a kagome lattice of cobalt ions and has triggered intense interest for rich fantastic phenomena. Here, we report the magnetic exchange couplings of Co3Sn2S2 using inelastic neutron scattering and two density functional theory (DFT) based methods: constrained magnetism and multiple-scattering Green's function methods. Co3Sn2S2 exhibits highly anisotropic magnon dispersions and linewidths below T-C, and paramagnetic excitations above T-C. The spin-wave spectra in the ferromagnetic ground state is well described by the dominant third-neighbor across-hexagon J(d) model. Our density functional theory calculations reveal that both the symmetry-allowed 120 degrees antiferromagnetic orders support Weyl points in the intermediate temperature region, with distinct numbers and the locations of Weyl points. Our study highlights the important role Co3Sn2S2 can play in advancing our understanding of kagome physics and exploring the interplay between magnetism and band topology.

Automated summary

The study of magnetic Weyl semimetal Co3Sn2S2 reveals its highly anisotropic magnetic properties and the presence of Weyl points in different temperature regions. Using density functional theory calculations, it is shown that the important role of the 120-degree antiferromagnetic order in supporting Weyl points in the intermediate temperature region.