General Scattering Mechanism and Transport in Graphene

Using quasi-time dependent semi-classical transport theory in RTA, we obtained coupled current equations in the presence of time varying field and based on general scattering mechanism $\tau \propto \mathcal{E}^{\beta}$. We find that close to the Dirac point, the characteristic exponent $\beta = +2$ corresponds to acoustic phonon scattering. $\beta = +1$ long-range Coulomb scattering mechanism. $\beta = -1$ is short-range delta potential scattering in which the conductivity is constant of temperature. The $\beta = 0$ case is ballistic limit. In the low energy dynamics of Dirac electrons in graphene, the effect of the time-dependent electric field is to alter just the electron charge by $e \to e(1 + (\Omega \tau)^2)$ making electronic conductivity non-linear. The effect of magnetic filed is also considered.Comment: 8 pages, 3 figure

Appearance of Negative Differential Conductivity in Graphene Nanoribbons at High-Harmonics

We theoretically study current dynamics of graphene nanoribbons subject to bias dc and ac driven fields. We showed that graphene nanoribbons exhibit negative high-harmonic differential conductivity. Negative differential conductivity appears when bias electric filed is in the neighborhood of applied ac filed amplitude. We also observe both even and odd high-harmonic negative differential conductivity at wave mixing of two commensurate frequencies. The even harmonics are more pronounced than the odd harmonics. A possible use of the present method for generating terahertz frequencies at even harmonics in graphene is suggested.Comment: 6 pages, 3 figure

Next-nearest-neighbor Tight-binding Model of Plasmons in Graphene

In this paper we investigate the influence of the next-nearest-neighbor coupling of tight-binding model of graphene on the spectrum of plasmon excitations. The nearest-neighbor tight-binding model was previously used to calculate plasmon spectrum in the next paper [1]. We expand the previous results of the paper by the next-nearest-neighbor tight-binding model. Both methods are based on the numerical calculation of the dielectric function of graphene and loss function. Here we compare plasmon spectrum of the next-nearest and nearest-neighbor tight-binding models and find differences between plasmon dispersion of two models.Comment: LaTeX, 4 pages, 4 Fig

Symmetry classification of energy bands in graphene and silicene

We present the results of the symmetry classification of the electron energy bands in graphene and silicene using group theory algebra and the tight--binding approximation. The analysis is performed both in the absence and in the presence of the spin-orbit coupling. We also discuss the bands merging in the Brillouin zone symmetry points and the conditions for the latter to become Dirac points.Comment: LaTeX, 6 pages, 2 eps Figures. A Figure and a citation were added. Accepted for publication in Graphen

Graphene-plasmon polaritons: From fundamental properties to potential applications

With the unique possibilities for controlling light in nanoscale devices, graphene plasmonics has opened new perspectives to the nanophotonics community with potential applications in metamaterials, modulators, photodetectors, and sensors. This paper briefly reviews the recent exciting progress in graphene plasmonics. We begin with a general description for optical properties of graphene, particularly focusing on the dispersion of graphene-plasmon polaritons. The dispersion relation of graphene-plasmon polaritons of spatially extended graphene is expressed in terms of the local response limit with intraband contribution. With this theoretical foundation of graphene-plasmon polaritons, we then discuss recent exciting progress, paying specific attention to the following topics: excitation of graphene plasmon polaritons, electron-phonon interactions in graphene on polar substrates, and tunable graphene plasmonics with applications in modulators and sensors. Finally, we seek to address some of the apparent challenges and promising perspectives of graphene plasmonics.Comment: Invited minireview paper on graphene plasmon polaritons, 11 pages, 4 figure