دکتر افشین مرادی

In this paper, the optical properties of a C60 molecule is studied within the framework of the quasi-static approximation. To do this, a C60 molecule is modeled by an infinitesimally thin spherical shell of the π and σ electrons and electronic excitations of this shell is described by means of the two-dimensional two-fluid hydrodynamic theory. At the first, general expression for polarizability of the system is obtained, by solving Laplace and hydrodynamic equations with appropriate boundary conditions. Then, by using the polarizability formula, the extinction spectrum of system is investigated which is in quite agreement with the result of the Mie theory. Also, the Maxwell-Garnett theory for the effective medium approximation of composite materials is developed to study the dielectric response of a composite of C60 molecules.

In this paper, by using the equivalent electrical circuit method, an analytical study for the electrical and dissipated energy densities in graphene is presented. In the first step, electronic excitations on the graphene surface are described by an infinitesimally thin layer of electron fluid, ignoring the electrons completely. Then, general expressions of electrical and dissipated energy densities are obtained by using a simple equation of motion for an electron of the electron fluid (that is subjected to a time dependent external electric field) in conjunction with the equivalent electrical circuit method. In the next step, in the range of high frequencies, by means of the conductivity formula of the system that is recently presented, the problem is investigated in a two-fluid model.