• Ajayan, Pulickel
• Zhang, Xiang
• Lin, Ming-Fu
• Fritz, David M.
• Kochat, Vidya
• Shen, Xiaozhe
• Weninger, Clemens
• Bergmann, Uwe
• Krishnamoorthy, Aravind
• Apte, Amey
• Vashishta, Priya
• Nakano, Aiichiro
• Shimojo, Fuyuki
• Li, Renkai
• Bassman, Lindsay
• Kalia, Rajiv
• Tiwary, Chandra Sekhar
• Zheng, Qiang

Abstract

Photo-induced non-radiative energy dissipation is a potential pathway to induce structural-phase transitions in two-dimensional materials. For advancing this field, a quantitative understanding of real-time atomic motion and lattice temperature is required. However, this understanding has been incomplete due to a lack of suitable experimental techniques. Here, we use ultrafast electron diffraction to directly probe the subpicosecond conversion of photoenergy to lattice vibrations in a model bilayered semiconductor, molybdenum diselenide. We find that when creating a high charge carrier density, the energy is efficiently transferred to the lattice within one picosecond. First-principles nonadiabatic quantum molecular dynamics simulations reproduce the observed ultrafast increase in lattice temperature and the corresponding conversion of photoenergy to lattice vibrations. Nonadiabatic quantum simulations further suggest that a softening of vibrational modes in the excited state is involved in efficient and rapid energy transfer between the electronic system and the lattice.

Topics

• density
• impedance spectroscopy
• molybdenum
• phase
• simulation
• electron diffraction
• semiconductor
• molecular dynamics
• phase transition
• two-dimensional