We find unusually large cross-polarized (and antisymmetric) Raman signature of ${\mathrm{A}}_{\mathrm{g}}$ phonon mode in ${\mathrm{CrI}}_3$, in agreement with experiments. The signal is present only when the following three effects are considered in concert: ferromagnetism on Cr atoms, spin-orbit interaction, and resonant effects. Somewhat surprisingly, we find that the relevant spin-orbit interaction potential originates from iodine atoms, despite magnetism being mostly on chromium atoms. We analyze the Raman signature as a function of magnetic order, the direction of the magnetic moment, energy, and polarization of light used for Raman scattering, as well as carrier lifetime. In addition to a strong cross-polarized Raman signal, we also find unusually strong phonon modulated magneto-optical Kerr effect (MOKE) in ${\mathrm{CrI}}_3$.

• Received 13 October 2020
• Accepted 5 February 2021

DOI:https://doi.org/10.1103/PhysRevMaterials.5.025202