Anisotropic Phonon Behavior and Phase Transition in Monolayer ReSe₂ Discovered by High Pressure Raman Scattering

Re-based transition metal dichalcogenides have attracted extensive attention owing to their anisotropic structure and excellent properties in applications such as optoelectronic devices and electrocatalysis. The present study methodically investigated the evolution of specific Raman phonon mode behaviors and phase transitions in monolayer and bulk ReSe₂ under high pressure. Considering the distinctive anisotropic characteristics and the vibration vectors of Re and Se atoms exhibited by monolayer ReSe₂, we perform phonon dispersion calculations and propose a methodology utilizing pressure-dependent polarized Raman measurements to explore the precise structural evolution of monolayer ReSe₂ under the stress fields. Varied behaviors of the E_g-like and A_g-like modes, along with their specific vector transformations, have been identified in the pressure range 0-14.59 GPa. The present study aims to offer original perspectives on the physical evolution of Re-based transition metal dichalcogenides, elucidating their fundamental anisotropic properties and exploring potential applicability in diverse devices.