期刊
PHYSICAL REVIEW LETTERS
卷 119, 期 3, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevLett.119.036803
关键词
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资金
- Max Planck Society
- European Research Council (ERC) under the European Union's Horizon research and innovation program [ERC-2015-CoG- 682843, ERC-2015-AdG-694097]
- Alexander von Humboldt Foundation
- People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7-PEOPLE-IEF [622934]
- Grupos Consolidados [IT578-13]
- Air Force Office of Scientific Research Award [FA2386-15-1-0006 AOARD 144088]
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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