title: Plasmon Excitations of Multi-layer Graphene on a Conducting Substrate.
abstract: We predict the existence of low-frequency nonlocal plasmons at the vacuum-surface interface of a superlattice of N graphene layers interacting with conducting substrate. We derive a dispersion function that incorporates the polarization function of both the graphene monolayers and the semi-infinite electron liquid at whose surface the electrons scatter specularly. We find a surface plasmon-polariton that is not damped by particle-hole excitations or the bulk modes and which separates below the continuum mini-band of bulk plasmon modes. The surface plasmon frequency of the hybrid structure always lies below ωs = ωp/√2, the surface plasmon frequency of the conducting substrate. The intensity of this mode depends on the distance of the graphene layers from the conductor's surface, the energy band gap between valence and conduction bands of graphene monolayer and, most importantly, on the number of two-dimensional layers. For a sufficiently large number of layers (N ≥ 7) the hybrid structure has no surface plasmon. The existence of plasmons with different dispersion relations indicates that quasiparticles with different group velocity may coexist for various ranges of wavelengths determined by the number of layers in the superlattice.
authors.affiliation: Department of Physics and Astronomy Hunter College of the City University of New York, 695 Park Avenue, New York, NY 10065 USA.|Donostia International Physics Center, P. Manuel de Lardizabal 4, 20018, San Sebastian, Spain.
authors.forename: Godfrey
authors.initials: G
authors.lastname: Gumbs
authors.affiliation: Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico, 87106, USA.
authors.forename: Andrii
authors.initials: A
authors.lastname: Iurov
authors.affiliation: Department of Physics, National Cheng Kung University, Tainan, Taiwan 701.
authors.forename: Jhao-Ying
authors.initials: JY
authors.lastname: Wu
authors.affiliation: Department of Physics, National Cheng Kung University, Tainan, Taiwan 701.
authors.forename: M F
authors.initials: MF
authors.lastname: Lin
authors.affiliation: US Military Academy, West Point, NY, U.S.A.
authors.forename: Paula
authors.initials: P
authors.lastname: Fekete