Chiral electronic excitations and strong electron-phonon coupling to Weyl fermions in the kagome semimetal Co₃Sn₂S₂

We present results of a Raman-scattering study of the Kagome ferromagnet Co₃Sn₂S₂, with a focus on electronic and phononic excitations and their interplay. We provide a theoretical analysis of the electronic-band structure, enabling a semiquantitative explanation of the spectra. A prominent feature in the electronic spectra is a redistribution of spectral weight from low to high energies in all polarization configurations starting at the Curie temperature T_C. In the symmetry-resolved spectra, the suppression of the A_1g continuum in the ferromagnetic state arises from the redistribution of electronic states below T_C, while a strong enhancement of the A_2g continuum is linked to the dynamics of fermions near the Fermi level E_F being characterized by spin-momentum locking near Weyl points. The A_1g phonon modulates the position of these Weyl points and couples strongly to the related fermions close to E_F. These results allow a comprehensive understanding of the bulk band-structure evolution as a function of temperature in Co₃Sn₂S₂, offering key insights for further studies of the driving force behind the long-range magnetic order and novel topological states in this compound.