Resonant electronic A_2g Raman scattering between the Weyl bands in Co₃Sn₂S₂

Co₃Sn₂S₂ is a semimetal with a ferromagnetic transition at T_C = 175 K. The strongly coupled Raman-active A_1g phonon exhibits a distinct maximum of the line width Γ (FWHM) and the Fano asymmetry parameter 1/|q| at T_C. Density functional theory (DFT) calculations  explain the related reduction of the electronic density of states (DOS) at the Fermi energy resulting from the band splitting. Below T_C, the electronic Raman spectra in A_2g symmetry show an isolated broad peak centered at 0.2 eV. Electronic excitations in the chiral A_2g symmetry require a spin flip and, thus, can only occur between the Weyl bands with spin-momentum locking. We show that resonant excitations between the lower and the upper Weyl bands through an intermediate p band reproduce the spectra semi-quantitatively as long as the Weyl points are sufficiently close to the Fermi surface. This proximity is in full agreement with the motion of the Weyl points in momentum space driven by the strongly coupling A_1g phonon as predicted by our DFT simulations.