Journal
NANO LETTERS
Volume 20, Issue 10, Pages 7152-7158Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.0c02474
Keywords
twisted graphene; terahertz radiation; photogalvanics
Categories
Funding
- Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) [SPP 2244 (GA501/17-1)]
- Volkswagen Stiftung Program [97738]
- IRAP program of the Foundation for Polish Science [MAB/2018/9]
- Russian Science Foundation [17-12-01265]
- Foundation for Advancement of Theoretical Physics and Mathematics (BASIS)
- Elemental Strategy Initiative by the MEXT, Japan [JPMXP0112101001]
- JSPS KAKENHI [JP20H00354]
- CREST, JST [JPMJCR15F3]
- Russian Science Foundation [20-12-18026] Funding Source: Russian Science Foundation
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We report on the observation of photogalvanic effects in tBLG with a twist angle of 0.6 degrees. We show that excitation of the tBLG bulk causes a photocurrent, whose sign and magnitude are controlled by the orientation of the radiation electric field and the photon helicity. The observed photocurrent provides evidence for the reduction of the point group symmetry in low twist-angle tBLG to the lowest possible one. The developed theory shows that the current is formed by asymmetric scattering in gyrotropic tBLG. We also detected the photogalvanic current formed in the vicinity of the edges. For both bulk and edge photocurrents, we demonstrate the emergence of pronounced oscillations upon variation of the gate voltage. The gate voltages associated with the oscillations correlate with peaks in resistance measurements. These are well explained by interband transitions between a multitude of isolated bands in tBLG.
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