The Initial Time-Delay Response of Reflectivity Changes in Photoexcited Two-Dimensional Layered Semiconductor 2H-MoTe2

Two-dimensional (2D) layered semiconductors such as molybdenum (Mo)- and tungsten (W)-based transition-metal dichalcogenides (TMDCs) have been model systems to explore various quantum many-body processes owing to the strong confinement of carriers and phonons in each atomic layer. The confinement effect in semiconductor TMDCs strongly modifies the electronic and optical properties via the generation of strongly bound excitons or large band-gap renormalization (BGR) in the presence of unbound electron-hole (e-h) plasma under irradiation of ultrashort intense laser pulses [1]. The generation of the e-h pairs and electron-phonon coupling in semiconductors generally appears immediately after photoexcitation within < 1 ps [2], [3]. Therefore, it is crucial to investigate the ultrafast optical response to gain insight into non-equilibrium quasiparticle dynamics in 2D semiconductors.