10.1021/acs.nanolett.9b01179.s001 Aravind Krishnamoorthy Aravind Krishnamoorthy Ming-Fu Lin Ming-Fu Lin Xiang Zhang Xiang Zhang Clemens Weninger Clemens Weninger Ruru Ma Ruru Ma Alexander Britz Alexander Britz Chandra Sekhar Tiwary Chandra Sekhar Tiwary Vidya Kochat Vidya Kochat Amey Apte Amey Apte Jie Yang Jie Yang Suji Park Suji Park Renkai Li Renkai Li Xiaozhe Shen Xiaozhe Shen Xijie Wang Xijie Wang Rajiv Kalia Rajiv Kalia Aiichiro Nakano Aiichiro Nakano Fuyuki Shimojo Fuyuki Shimojo David Fritz David Fritz Uwe Bergmann Uwe Bergmann Pulickel Ajayan Pulickel Ajayan Priya Vashishta Priya Vashishta Optical Control of Non-Equilibrium Phonon Dynamics American Chemical Society 2019 dynamic far-from-equilibrium vibration modes femtosecond mega-electronvolt electron diffraction experiments phonon populations non-radiative energy relaxation pathways Non-Equilibrium Phonon Dynamics excitation understanding electron diffraction patterns light-induced 2019-06-24 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Optical_Control_of_Non-Equilibrium_Phonon_Dynamics/8411534 The light-induced selective population of short-lived far-from-equilibrium vibration modes is a promising approach for controlling ultrafast and irreversible structural changes in functional nanomaterials. However, this requires a detailed understanding of the dynamics and evolution of these phonon modes and their coupling to the excited-state electronic structure. Here, we combine femtosecond mega-electronvolt electron diffraction experiments on a prototypical layered material, MoTe<sub>2</sub>, with non-adiabatic quantum molecular dynamics simulations and <i>ab initio</i> electronic structure calculations to show how non-radiative energy relaxation pathways for excited electrons can be tuned by controlling the optical excitation energy. We show how the dominant intravalley and intervalley scattering mechanisms for hot and band-edge electrons leads to markedly different transient phonon populations evident in electron diffraction patterns. This understanding of how tuning optical excitations affect phonon populations and atomic motion is critical for efficiently controlling light-induced structural transitions of optoelectronic devices.