Terahertz nanoscopy of quantum-geometric photovoltaics in bilayer graphene
Abstract
The bulk photovoltaic effect (BPVE) provides a direct link between quantum geometry and nonlinear light-matter interactions, yet conventional far-field measurements cannot disentangle BPVE from contact- and interface-induced photothermoelectric signals. Here we develop cryogenic, polarization-sensitive terahertz microscopy with deep-subwavelength resolution and apply it to dual-gated AB bilayer graphene. Near resonance between the band gap and terahertz photon energy, we observe enhanced optical conductivity and spatially resolved BPVE. Polarization-dependent measurements reveal a characteristic twofold angular symmetry and a distinct shift-vector direction, both governed by crystalline symmetries and quantum geometry. The evolution of BPVE with carrier density and temperature provides a sensitive probe of the fine electronic structure of bilayer graphene, revealing signatures of trigonal warping and electron-hole asymmetry. Agreement with theory demonstrates that the terahertz nanoscopy of BPVE established here offers an optical lens into the interplay between band and quantum geometry in quantum materials.
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BibTeX
@misc{borodin2026terahertz,
title = {{Terahertz nanoscopy of quantum-geometric photovoltaics in bilayer graphene}},
author = {Bogdan Borodin and Jiangxu Li and Xuanpu Zhang and Aleksei Karaborchev and Som Subhra Guria and Kenji Watanabe and Takashi Taniguchi and Roshan Krishna Kumar and Fan Zhang and Petr Stepanov},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.05620},
eprint = {2610.05620},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.05620},
}
RIS
TY - UNPB
TI - Terahertz nanoscopy of quantum-geometric photovoltaics in bilayer graphene
AU - Bogdan Borodin
AU - Jiangxu Li
AU - Xuanpu Zhang
AU - Aleksei Karaborchev
AU - Som Subhra Guria
AU - Kenji Watanabe
AU - Takashi Taniguchi
AU - Roshan Krishna Kumar
AU - Fan Zhang
AU - Petr Stepanov
PY - 2026
DA - 2026/10/04
PB - arXiv
DO - 10.48550/arxiv.2610.05620
UR - https://arxiv.org/abs/2610.05620
AB - The bulk photovoltaic effect (BPVE) provides a direct link between quantum geometry and nonlinear light-matter interactions, yet conventional far-field measurements cannot disentangle BPVE from contact- and interface-induced photothermoelectric signals. Here we develop cryogenic, polarization-sensitive terahertz microscopy with deep-subwavelength resolution and apply it to dual-gated AB bilayer graphene. Near resonance between the band gap and terahertz photon energy, we observe enhanced optical conductivity and spatially resolved BPVE. Polarization-dependent measurements reveal a characteristic twofold angular symmetry and a distinct shift-vector direction, both governed by crystalline symmetries and quantum geometry. The evolution of BPVE with carrier density and temperature provides a sensitive probe of the fine electronic structure of bilayer graphene, revealing signatures of trigonal warping and electron-hole asymmetry. Agreement with theory demonstrates that the terahertz nanoscopy of BPVE established here offers an optical lens into the interplay between band and quantum geometry in quantum materials.
ER -