Ultrafast Electron-Phonon and Phonon-Phonon Interactions in Multilayer 2H-MoTe₂

Transition metal dichalcogenides are emerging novel functional materials for many potential applications. However, its fundamental properties and physics at a short time scale is still unclear. Here, we used the ultrafast electron diffraction to investigate the nonradiative process such as electron-phonon and phonon-phonon interactions with a temporal resolution of ~200 fs. A multilayer 2H-MoTe₂ was photoexcited at 400 nm and 800 nm, respectively, to create a high carrier density, leading to a temperature jump of tens of kelvin. A strong diffuse scattering appears in the diffraction pattern in a picosecond time scale, implying a fast and effecient electron-phonon interaction. We also observed an anisotropic population of phonon branches specifically located at M-point, corresponding to the Mo-Mo dimerization coordinate. The nonadiabatic quantum molecular dynamics (NAQMD) simulation was incorporated to disentangle the complex light-induced structure disorder dynamics, which also sheds new light on light-driven structure phase transition for 2D materials.