Revealing quantum geometry effects in magic angle twisted bilayer graphene using the circular photogalvanic effect
Abstract
Magic-angle twisted bilayer graphene (MATBG) hosts flat bands whose correlated and topological phases depend sensitively on the electronic point-group symmetry, which is set by the device configuration including twist angle, heterostrain, and substrate and cap-layer coupling. Here we report near-infrared photocurrent measurements of a MATBG device encapsulated by an hBN substrate and a WSe2 cap layer, at a twist angle of 1.05°. Using spatially resolved photocurrent imaging with polarization analysis, we disentangle the photothermoelectric response from the circular photogalvanic effect (CPGE) across all fillings of the moiré flat bands. A finite CPGE at normal incidence, forbidden in high-symmetry structures, directly constrains the point-group symmetry of MATBG and reveals a Berry curvature dipole intrinsic to the MATBG flat bands, activated by the symmetry lowering from heterostrain and the asymmetric hBN/WSe2 environment. Our results establish nonlinear photocurrent as an all-optical probe of symmetry and quantum geometry in proximity-engineered moiré materials.
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BibTeX
@misc{persky2026revealing,
title = {{Revealing quantum geometry effects in magic angle twisted bilayer graphene using the circular photogalvanic effect}},
author = {Eylon Persky and Leonie Parisot and Minhao He and Jiaqi Cai and Takashi Taniguchi and Kenji Watanabe and Pierre A. Pantaleon and Francisco Guinea and Xiaodong Xu and Aharon Kapitulnik},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2606.06389},
eprint = {2606.06389},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.06389},
}
RIS
TY - UNPB
TI - Revealing quantum geometry effects in magic angle twisted bilayer graphene using the circular photogalvanic effect
AU - Eylon Persky
AU - Leonie Parisot
AU - Minhao He
AU - Jiaqi Cai
AU - Takashi Taniguchi
AU - Kenji Watanabe
AU - Pierre A. Pantaleon
AU - Francisco Guinea
AU - Xiaodong Xu
AU - Aharon Kapitulnik
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2606.06389
UR - https://arxiv.org/abs/2606.06389
AB - Magic-angle twisted bilayer graphene (MATBG) hosts flat bands whose correlated and topological phases depend sensitively on the electronic point-group symmetry, which is set by the device configuration including twist angle, heterostrain, and substrate and cap-layer coupling. Here we report near-infrared photocurrent measurements of a MATBG device encapsulated by an hBN substrate and a WSe_2 cap layer, at a twist angle of 1.05°. Using spatially resolved photocurrent imaging with polarization analysis, we disentangle the photothermoelectric response from the circular photogalvanic effect (CPGE) across all fillings of the moiré flat bands. A finite CPGE at normal incidence, forbidden in high-symmetry structures, directly constrains the point-group symmetry of MATBG and reveals a Berry curvature dipole intrinsic to the MATBG flat bands, activated by the symmetry lowering from heterostrain and the asymmetric hBN/WSe_2 environment. Our results establish nonlinear photocurrent as an all-optical probe of symmetry and quantum geometry in proximity-engineered moiré materials.
ER -