Near-field Measurements of Magneto-edge-plasmon of Graphene

Surface plasmon polariton confines long-wavelength electromagnetic waves to nanometer scale on the interface of a metal and an insulator. The wide tunability and high quality-factor of polariton modes are keys to observe a plethora of quantum effects involving strong light-matter interaction. At low temperature, graphene has been shown to host plasmon polaritons with a long lifetime, which enables graphene plasmons to probe interfacial properties of neighboring materials. Under magnetic field, the plasmon, gapped by cyclotron frequency, becomes topologically nontrivial magneto-plasmon, which contributes to a gapless edge state called magneto-edge-plasmon (MEP). The low damping rate, topological protection, and non-reciprocity of MEP gives rise to a unique propagating pattern. In this talk, we discuss the observation of the magneto-edge-plasmon in both near-field scattering and nano-photocurrent signal using the state-of-the-art magnetic scanning near-field optical microscope (m-SNOM).