Abstract
We report on the direct observation of electron transfer between the surface and the second layer of the prototypical transition-metal dichalcogenide . We are able to disentangle the excitation and the transfer process in our measurement. Thereby, we determine both the momentum location and the duration of the electron transfer between the first two layers. Our -based tight-binding calculations reveal that the band gap in the surface layer is considerably larger than in deeper layers and that the coupling between surface and deeper layers is strongly momentum-dependent throughout the Brillouin zone. At the conduction-band minimum we find strong coupling, which explains the ultrafast interlayer charge transfer observed in our experiment at this location.
- Received 20 March 2020
- Revised 17 August 2020
- Accepted 20 August 2020
DOI:https://doi.org/10.1103/PhysRevB.102.125417
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