Optical Control of Non-Equilibrium Phonon Dynamics
A Krishnamoorthy and MF Lin and X Zhang and C Weninger and RR Ma and A Britz and CS Tiwary and V Kochat and A Apte and J Yang and S Park and RK Li and XZ Shen and XJ Wang and R Kalia and A Nakano and F Shimojo and D Fritz and U Bergmann and P Ajayan and P Vashishta, NANO LETTERS, 19, 4981-4989 (2019).
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, MoTe2, with non-adiabatic quantum molecular dynamics simulations and ab initio 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.
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