Sub‐Nanometer Curvature Unlocks Quantum Orbital Flexoelectricity in Graphene

Abstract

ABSTRACT Flexoelectricity, defined as polarization induced by strain gradients, is especially pronounced in two‐dimensional (2D) materials due to their mechanical flexibility and sensitivity to deformation. In nanostructures with nanometer‐scale curvature, bending can perturb out‐of‐plane π orbitals and generate quantum‐mechanical polarization and electrostatic modulation beyond classical lattice distortion alone. Here, we combine scanning probe measurements and first‐principles calculations to provide experimental and theoretical evidence for large intrinsic quantum orbital flexoelectricity in graphene nanowrinkles (GNWrs) with estimated polarization densities of P th ∼ 4 C m −2 and P exp ∼ 1 C m −2 , exceeding those of mesoscale systems by 5 to 7 orders of magnitude. These GNWrs exhibit high apex curvature, undergo atomic‐level buckling, and produce localized strain fields, as supported by atomic force microscopy analysis and Raman spectroscopy. Kelvin probe force microscopy reveals curvature‐dependent work‐function shifts, while conductive atomic force microscopy detects reproducible GNWr‐associated currents with a threshold voltage ( Φ th ∼ 1 V) comparable to the band offset predicted by ab initio calculations (∼ 1.2 V). These results support an interpretation in which curvature‐induced flexoelectric dipoles reshape the local electronic potential. GNWrs therefore provide a structurally simple carbon‐based platform for probing quantum‐mechanical flexoelectricity.