Abstract
The propagation of an electron beam over a graphene/dielectric sandwich structure is considered assuming the distance between the graphene layers in sandwich is large enough to prevent interlayer tunneling. A dispersion equation for the surface electromagnetic modes propagating along graphene sheets is derived and \ifmmode \check{C}\else \v{C}\fi{}erenkov synchronism between a surface wave and a nonrelativistic electron beam is predicted at achievable parameters of the system. Generation frequency tuning is proposed by varying the graphene doping, the number of graphene sheets, the distance between sheets, etc.
Highlights
Due to a variety of scientific and technical applications, there is a great need in the development of coherent terahertz radiation sources with tunable frequency, see e.g. Refs. 1,2 and references therein
In the present paper we study excitation of surface waves propagating in graphene sandwich structures and resonantly interacting with an electron beam, aiming at the reveal of the generation conditions and methods of the smooth frequency tuning by variation of the system parameters
The dependence of the Cerenkov resonant frequency ν on chemical potential is depicted on Fig. 3 at different values of the electron beam energy
Summary
Due to a variety of scientific and technical applications, there is a great need in the development of coherent terahertz radiation sources with tunable frequency, see e.g. Refs. 1,2 and references therein. Similar effect can be achieved by hybridization of graphene plasmon with its mirror image in the metal plate disposed near graphene layer that leads, in particular, to strongly confined asymmetric mode[45,46] As it has been stressed in Ref.[14], a combination in graphene and CNTs of three key properties, (i) ballisticity of the electron flow over typical length, (ii) extremely high current-carrying capacity, and (iii) strong slowing down of surface electromagnetic waves[9], allows proposing them as candidates for the development of nano-sized Cernekov-type emitters. Both these effects give possibility to regulate the generated frequency and resonance electron beam energy. VI contains analysis concerning possibilities of generation and frequency tuning based on previous calculations and conclusion remarks
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