Graphene plasmons possess a number of unique optical properties and have been demonstrated to enable a variety of applications in the THz frequency range and the infrared frequency range, where active tunability through electrostatic gating plays an important role. In addition, graphene plasmons can be tuned by a static magnetic field, resulting in so called graphene magnetoplasmons. Here, we investigate the excitation of magnetoplasmons in graphene nanostructures with different shapes. We show that in the presence of a static magnetic field, plasmonic dipolar modes will split and the splitting is symmetrical in regular polygons. The splitting depends not on the size but only on the number of sides of the regular polygons. Larger splitting will occur in regular polygons with more sides, where the maximum splitting is achieved in circular disks. We further introduce a simple Lorentz model that could provide an excellent description of optical excitations in regular polygons. Finally, we examine the magnetoplasmons in the shapes without rotational symmetry, such as rectangles, where the symmetry of the splitting breaks as well.

• Received 30 November 2018

DOI:https://doi.org/10.1103/PhysRevB.99.195447