期刊
NANO LETTERS
卷 20, 期 6, 页码 4631-4637出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.0c01519
关键词
Exciton; vdW heterostructures; ultrafast dynamics; TD-DFT
类别
资金
- National Science Foundation [DMR1828019]
- Army Research Office [W911NF1810473]
- U.S. Department of Defense (DOD) [W911NF1810473] Funding Source: U.S. Department of Defense (DOD)
Recent experiments revealed stacking-configuration-independent and ultrafast charge transfer in transition metal dichalcogenides van der Waals (vdW) heterostructures, which is surprising given strong exciton binding energies and large momentum mismatch across the heterojunctions. Previous theories failed to provide a comprehensive physical picture for the charge transfer mechanisms. To address this challenge, we developed a first-principles framework which can capture exciton-phonon interaction in extended systems. We find that excitonic effect does not impede, but actually drives ultrafast charge transfer in vdW heterostructures. The many-body electron-hole interaction affords cooperation among the electrons, which relaxes the constraint on momentum conservation and reduces energy gaps for charge transfer. We uncover a two-step process in exciton dynamics: ultrafast hole transfer followed by much longer relaxation of intermediate hot excitons. This work establishes that many-body excitonic effect is crucial to the ultrafast dynamics and provides a basis to understand relevant phenomena in vdW heterostructures.
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