Ivan Radović

High-energy plasmon spectroscopy of freestanding multilayer graphene

We present several applications of the layered electron gas model to electron energy loss spectroscopy of freestanding films consisting of

Probing the Plasmon-Phonon Hybridization in Supported Graphene by Externally Moving Charged Particles

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Analytical modeling of electron energy loss spectroscopy of graphene: Ab initio study versus extended hydrodynamic model

graphene layers in a scanning transmission electron microscope. Using a two-fluid model for the single-layer polarizability, we discuss the evolution of high-energy plasmon spectra with

Channeling of fast ions through the bent carbon nanotubes: The extended two-fluid hydrodynamic model*

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Excitation of plasmon wakes in two-dimensional electron systems by moving external charged particles

and find good agreement with the recent experimental data for both multilayer graphene with

Carbon nanotubes characterization by channeled fast ions spatial and angular distribution fingerprints

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Wake effect in graphene due to moving charged particles

and thick slabs of graphite. Such applications of these analytical models help shed light on several features observed in the plasmon spectra of those structures, including the role of plasmon dispersion, dynamic interference in excitations of various plasmon eigenmodes, as well as the relevance of the bulk plasmon bands, rather than surface plasmons, in classifying the plasmon peaks.

Interactions of ions with graphene

We use the dielectric response formalism to show how an incident charged particle may be used to probe the hybridization taking place between the Dirac plasmon in graphene and the surface optical phonon modes in a SiO2 substrate. Strong effects of this hybridization are found in the wake pattern in the induced potential, as well as in the stopping and image forces that act on the incident charge in a broad range of its velocities. Particularly intriguing is the possibility to control the plasmon-phonon hybridization by varying the doping density of graphene, where the regime of a nominally neutral graphene is expected to give rise to dramatic effects in the energy loss of charged particles that move at the velocities below the Fermi velocity of graphene.

Dispersion and damping of the interband π plasmon in graphene grown on Cu(111) foils

We present an analytical modeling of the electron energy loss (EEL) spectroscopy data for free-standing graphene obtained by scanning transmission electron microscope. The probability density for energy loss of fast electrons traversing graphene under normal incidence is evaluated using an opticalxa0approximation based on the conductivity of graphene given in the local, i.e., frequency-dependent form derived by both a two-dimensional, two-fluid extended hydrodynamic (eHD) model and an ab initio method. We compare the results for the real and imaginary parts of the optical conductivity in graphene obtained by these two methods. The calculated probability density is directly compared with the EEL spectra from three independent experiments and we find very good agreement, especially in the case of the eHD model. Furthermore, we point out that the subtraction of the zero-loss peak from the experimental EEL spectra has a strong influence on the analytical model for the EEL spectroscopy data.

Interband plasmons in supported graphene on metal substrates: Theory and experiments

We investigate the interactions of charged particles with straight and bent single-walled carbon nanotubes (SWNTs) under channeling conditions in the presence of dynamic polarization of the valence electrons in carbon. This polarization is described by a cylindrical, two-fluid hydrodynamic model with the parameters taken from the recent modelling of several independent experiments on electron energy loss spectroscopy of carbon nano-structures. We use the hydrodynamic model to calculate the image potential for protons moving through four types of SWNTs at a speed of 3 atomic units. The image potential is then combined with the Doyle–Turner atomic potential to obtain the total potential in the bent carbon nanotubes. Using that potential, we also compute the spatial and angular distributions of protons channeled through the bent carbon nanotubes, and compare the results with the distributions obtained without taking into account the image potential.