Phonon Dynamics\nin MnPSe<sub>3</sub> Studied by Raman\nSpectroscopy and First-Principles Calculations

In contrast to well-studied sulfides in the category\nof van der\nWaals transition-metal phosphorus trichalcogenides MPX<sub>3</sub>, the intrinsic phonon properties of the antiferromagnetic semiconducting\nmaterial of MnPSe<sub>3</sub> remain unclear, which is crucial for\nexploiting its emerging applications. In this study, we present comprehensive\nangle-resolved polarized and temperature-dependent Raman spectroscopy\nmeasurements conducted on single crystals of MnPSe<sub>3</sub>, with\nthe aid of group theory analysis and first-principles calculations.\nAll of the experimentally observed Raman modes are systematically\nassigned. The thermal expansion coefficient for MnPSe<sub>3</sub> is\ncarefully determined using the quasi-harmonic approximation method.\nFurther insight into the temperature-dependent red shift of phonon\npeaks and nonlinear broadening of line widths is obtained through\na detailed theoretical model analysis, revealing their association\nwith the anharmonic phonon–phonon interactions. Specifically,\nrobust four-phonon scattering channels are identified, providing a\ndeeper understanding of phonon heat transport in MPX<sub>3</sub> materials.