Year: 2026
Type: preprint
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.
Source: arXiv (Cornell University)
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: G1450738401, G2442584775, Collaborative Research: Correlated Phases in an Unusual Family of Crystalline 2D Materials, G4162329948, G4806815962, G6004699919, Collaborative Research: DMREF: Developing and Harnessing the Platform of Quasi-One-Dimensional Topological Materials for Novel Functionalities and Devices, G898758523, CAREER: Towards a Unified Optical View of Strong Correlation in Moire Quantum Matter
OpenAlex ID: W7220692051