Polarized Raman spectroscopy on topological semimetal Co₃Sn₂S₂

概要

We present polarized Raman spectroscopy of the topological semimetal Co3Sn2S2, which was recently shown to host a Weyl semimetal phase. Stokes Raman spectra were obtained with the incident light parallel to the c-axis of Co3Sn2S2. Two major phonon Raman peaks were observed at 289 and 386 cm(-1) over continuous background emission signals. The intensity of the low-wavenumber (289 cm(-1)) peak showed no polarization dependence. The high-wavenumber (386 cm(-1)) peak and the continuous background signal were strongly polarized in the incident light polarization direction. These responses were almost independent of the in-plane crystal orientation to the incident polarization, as is the manifestation of the D3d$$ {D}_{3d} $$ point group symmetry of the unit cell of Co3Sn2S2. According to the group theory and Raman tensor analyses, the low- and high-wavenumber Raman signals are attributed to Gamma point phonon modes with Eg$$ {E}_g $$ and A1g$$ {A}_{1g} $$ symmetries, respectively. Furthermore, line shape analyses revealed that the high-wavenumber A1g$$ {A}_{1g} $$ mode exhibited asymmetric peak feature well described by the Breit-Wigner-Fano function. These results suggest the Fano resonance between the A1g$$ {A}_{1g} $$ phonon scattering with the continuous electronic background associated with low energy excitations near the Fermi energy. The clarified phonon energies and symmetries, as well as the electronic contribution to the Raman scattering, will not only be useful as a fingerprint to readily verify the experimentally grown or theoretically calculated crystal structure but also suggest importance of Raman spectroscopy as an effective tool to study low energy excitations and their interactions in Co3Sn2S2.

この論文で使われている画像