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Momentum-Resolved View of Electron-Phonon Coupling in Multilayer WSe2

Abstract : We investigate the interactions of photoexcited carriers with lattice vibrations in thin films of the layered transition metal dichalcogenide (TMDC) WSe2. Employing femtosecond electron diffraction with monocrystalline samples and first-principles density functional theory calculations, we obtain a momentum-resolved picture of the energy transfer from excited electrons to phonons. The measured momentum-dependent phonon population dynamics are compared to first-principles calculations of the phonon linewidth and can be rationalized in terms of electronic phase-space arguments. The relaxation of excited states in the conduction band is dominated by intervalley scattering between Sigma valleys and the emission of zone boundary phonons. Transiently, the momentum-dependent electron-phonon coupling leads to a nonthermal phonon distribution, which, on longer time scales, relaxes to a thermal distribution via electron-phonon and phonon-phonon collisions. Our results constitute a basis for monitoring and predicting out of equilibrium electrical and thermal transport properties for nanoscale applications of TMDCs.
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https://hal-univ-rennes1.archives-ouvertes.fr/hal-01578404
Contributor : Laurent Jonchère <>
Submitted on : Tuesday, August 29, 2017 - 10:40:12 AM
Last modification on : Monday, March 2, 2020 - 4:09:36 PM

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L. Waldecker, Roman Bertoni, H. Huebener, T. Brumme, T. Vasileiadis, et al.. Momentum-Resolved View of Electron-Phonon Coupling in Multilayer WSe2. Physical Review Letters, American Physical Society, 2017, 119 (3), pp.036803. ⟨10.1103/PhysRevLett.119.036803⟩. ⟨hal-01578404⟩

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