Fano Resonance Enabled Infrared Nano-Imaging of Local Strain in Bilayer Graphene

Detection of local strain at the nanometer scale with high sensitivity remains challenging. Here we report near-field infrared nano-imaging strains in bilayer graphene by probing strain-induced shifts phonon frequency. As a non-polar crystal, intrinsic possesses little response its transverse optical The reported detection is enabled applying vertical electrical field that breaks symmetry two layers and introduces finite dipole moment to phonon. activated further interacts continuum electronic transitions, generates strong Fano resonance. resulted resonance features very sharp scattering peak, which leads an extraordinary ∼ 0.002% for detection. Our results demonstrate first nano-scale resonance, provide new way probe crystals, open exciting possibilities studying rich phenomena.