Effects of screening on the propagation of graphene surface plasmons

We investigated surface plasmons in epitaxial graphene, while paying particular attention to the effect of interface states and resistivity on the transport properties[1,2]. The propagation velocity of the surface plasmons is much slower than the electron Fermi velocity when the screening effect provided by interface states is taken into account. Furthermore, slow-moving surface plasmons undergo a strong diffusion when the Fermi energy is near the Dirac point. This is shown by a numerical simulation of an RLC circuit model and its continuum approximation known as the telegrapher's equation. We could explain recent experimental results for the surface plasmons satisfactorily. [1] Kumada {\it et al.}, New J. Phys. {\bf 16}, 063055 (2014). [2] Sasaki and Kumada, Phys. Rev. B {\bf 90}, 035449 (2014).