Planar rotation of electric field induced by edge-plasmon in a graphene nanoribbon

The presence of an edge in a two-dimensional (2D) material can induce an accumulation of charges near the edge by the electric field. Similar to the 2D plasmon, the accumulated charges can oscillate collectively, forming a distinct plasmon mode, which is called edge-plasmon. In contrast to the 2D plasmon, the electric potential of the edge-plasmon is localized near the edge. In this work, we discuss the edge-plasmon in a 2D material with finite width, such as a graphene nanoribbon, and we find that the localization of the electric field to the edge induces a phase difference of π/2 between electric fields in the directions parallel and perpendicular to the edge. As a result, the induced electric field rotates on the surface and also induces rotating current, which does not exist in the 2D plasmon. The edge-plasmon can be excited by incident light, and we predict that the rotating current generates rotation of the electric field of the scattered light.