Raman scattering study of two-dimensional magnetic van der Waals compound VI3 *

Abstract

The layered magnetic van der Waals materials have generated tremendous interest due to their potential applications and importance in fundamental research. Previous x-ray diffraction (XRD) studies on the magnetic van der Waals compound VI3, revealed a structural transition above the magnetic transition but output controversial analysis on symmetry. In this paper we carried out polarized Raman scattering measurements on VI3 from 10 K to 300 K, with focus on the two A g phonon modes at ∼ 71.1 cm−1 and 128.4 cm−1. Our careful symmetry analysis based on the angle-dependent spectra demonstrates that the crystal symmetry can be well described by C 2h rather than D 3d both above and below structural phase transition. We further performed temperature-dependent Raman experiments to study the magnetism in VI3. Fano asymmetry and anomalous linewidth drop of two A g phonon modes at low temperatures, point to a significant spin–phonon coupling. This is also supported by the softening of 71.1-cm−1 mode above the magnetic transition. The study provides the fundamental information on lattice dynamics and clarifies the symmetry in VI3. And spin–phonon coupling existing in a wide temperature range revealed here may be meaningful in applications.