Plasmon Generation through Electron Tunneling in Graphene

The short wavelength of graphene plasmons relative to the light wavelength makes them attractive for applications in optoelectronics and sensing. However, this property limits their coupling to external light and our ability to create and detect them. More efficient ways of generating plasmons are therefore desirable. Here we demonstrate through realistic theoretical simulations that graphene plasmons can be efficiently excited via electron tunneling in a sandwich structure formed by two graphene monolayers separated by a few atomic layers of hBN. We obtain plasmon generation rates of $\sim10^{12}-10^{14}/$s over an area of the squared plasmon wavelength for realistic values of the spacing and bias voltage, while the yield (plasmons per tunneled electron) has unity order. Our results support electrical excitation of graphene plasmons in tunneling devices as a viable mechanism for the development of optics-free ultrathin plasmonic devices.Comment: 15 pages, 11 figures, 92 reference

Interaction of radiation and fast electrons with clusters of dielectrics: A multiple scattering approach

4 pages, 3 figures.-- PACS numbers: 73.20.Mf, 41.20.Jb, 61.16.Bg, 61.46.+wA fast, accurate, and general technique for solving Maxwell's equations in arbitrarily disposed clusters of dielectric objects is presented, based upon multiple scattering of electromagnetic multipole fields. Examples of application to the simulation of electron energy loss, radiation emission induced by fast electrons, and light scattering are offered. Large rates of Smith-Purcell radiation are predicted in the interaction of fast electrons with strings of Al and SiO2 spheres, suggesting its possible application in tunable soft UV light generation. Mutual electromagnetic interaction among objects in the different clusters under consideration is shown to be of primary importance.Help and support from the University of the Basque Country, the Spanish Ministerio de Educación y Cultura under Fulbright Grant No. FU-98-22726216, and the U.S. DOE under Contract No. DE-AC03-76SF00098 are gratefully acknowledged.Peer reviewe

Relativistic description of valence energy losses in the interaction of fast electrons with clusters of dielectrics: Multiple-scattering approach

A fully relativistic description of valence energy losses suffered by fast electrons passing near finite clusters of arbitrarily disposed dielectric objects is presented using an accurate technique suited to solve Maxwell’s equations. The method is based upon an expansion of the electromagnetic field in terms of multipoles around each of the objects of the cluster. Multiple elastic scattering of those multipole expansions is then performed until convergence is achieved. The energy loss, obtained from the induced electric field acting back on the electron, is computed in a time proportional to the square of the number of objects in the cluster, N2. Numerical examples are presented for various clusters formed by N=1–198 homogeneous spheres made of SiO2 and Al, and also for clusters of Si spheres coated with SiO2. Both relativistic effects and the interaction between the constituents of the cluster are shown to be of primary importance in the understanding of the position and magnitude of the features exhibited by the calculated electron-energy-loss spectra.Help and support from the University of the Basque Country and the Spanish Ministerio de Educacion y Cultura, under Fulbright Grant No. FU-98-22726216, is gratefully acknowledged. Part of this work was supported by the U.S. Department of Energy under contract No. DEAC03-76SF00098.Peer reviewe