Journal
NANO LETTERS
Volume 22, Issue 15, Pages 6069-6074Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.2c00905
Keywords
graphene; Raman spectroscopy; atomistic modeling; electron-phonon interaction
Categories
Funding
- CNPq [302775/2018-8]
- CAPES [88881.198744/2018-01]
- FAPEMIG, Brazil
- DoE [DE-SC0008807]
- Federation Wallonie-Bruxelles through the ARC [16/21-077, 21/26-116]
- European Union [881603]
- Flag-Era JTC project TATTOOS [R.8010.19]
- EOS project CONNECT [40007563]
- Belgium F.R.S.-FNRS [T.0051.18, T.029.22]
- NY State Empire State Development's Division of Science, Technology, and Innovation (NYSTAR)
- F.R.S.-FNRS of Belgium [2.5020.11]
- U.S. Department of Energy (DOE) [DE-SC0008807] Funding Source: U.S. Department of Energy (DOE)
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This study investigates the importance of phonons in twisted-bilayer graphene at the magic-angle using gate-dependent micro-Raman spectroscopy. The results reveal that the unique electronic structure at the magic-angle influences the electron-phonon coupling, resulting in a larger G band line width.
The importance of phonons in the strong correlation phenomena observed in twisted-bilayer graphene (TBG) at the so-called magic-angle is under debate. Here we apply gate-dependent micro-Raman spectroscopy to monitor the G band line width in TBG devices of twist angles theta = 0 degrees (Bernal), similar to 1.1 degrees (magic-angle), and similar to 7 degrees (large-angle). The results show a broad and p-/n-asymmetric doping behavior at the magic angle, in clear contrast to the behavior observed in twist angles above and below this point. Atomistic modeling reproduces the experimental observations in close connection with the joint density of electronic states in the electron-phonon scattering process, revealing how the unique electronic structure of magic-angle TBGs influences the electron-phonon coupling and, consequently, the G band line width. Overall, the value of the G band line width in magic-angle TBG is larger when compared to that of the other samples, in qualitative agreement with our calculations.
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