A corner reflector of graphene Dirac fermions as a phonon-scattering sensor

• Main Authors: Graef, Holger, Teo, Edwin Hang Tong, Wilmart, Q., Rosticher, M., Mele, D., Banszerus, L., Stampfer, C., Taniguchi, T., Watanabe, K., Berroir, J.-M., Bocquillon, E., Fève, G., Plaçais, B.
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2019
• Subjects: Nanoscience and Technology; Physics; Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/107512; http://hdl.handle.net/10220/49731
• Institution: Nanyang Technological University

Dirac fermion optics exploits the refraction of chiral fermions across optics-inspired Klein-tunneling barriers defined by high-transparency p-n junctions. We consider the corner reflector (CR) geometry introduced in optics or radars. We fabricate Dirac fermion CRs using bottom-gate-defined barriers in hBN-encapsulated graphene. By suppressing transmission upon multiple internal reflections, CRs are sensitive to minute phonon scattering rates. Here we report on doping-independent CR transmission in quantitative agreement with a simple scattering model including thermal phonon scattering. As a signature of CRs, we observe Fabry-Pérot oscillations at low temperature, consistent with single-path reflections. Finally, we demonstrate high-frequency operation which promotes CRs as fast phonon detectors. Our work establishes the relevance of Dirac fermion optics in graphene and opens a route for its implementation in topological Dirac matter.