Photo-induced Subpicosecond Temperature Jump in MoSe$_{\mathrm{2}}$ bilayer*

We observed sub-picosecond dynamics of lattice vibration in MoSe$_{\mathrm{2}}$ bilayer initiated by optical excitations at 800 nm and 400 nm, respectively, at high electron-hole plasma density. These photoinduced dynamics are probed by a delayed mega-electronvolt ultrafast electron diffraction (MeV-UED) that allows us to measure the conversion of electronic energy of carriers to in-plane lattice motion in real time. Corresponding ultrafast dynamics of lattice vibration is different from the irreversible inertial atomic acceleration model. Efficient electronic energy conversion to lattice motion signifies the possibility of light-induced approach for controllable temperature jump for future application in phase patterning of few-layered devices using transition metal dichalcogenides.