Dynamic polarization of graphene by external correlated charges

Abstract

We use the dielectric response formalism within random phase approximation for graphenes pi-electron bands to study polarization of doped, single-layer graphene in the presence of a moving dipole and a pair of comoving ions, as well as to study the electrostatic part of the long-range interaction in the coadsorption of two ions and two dipoles on graphene. We find that the vector components of both the force and the torque on the moving dipole include both the conservative and dissipative contributions, whereas the wake in the induced charge density in graphene shows asymmetry with respect to the direction of dipoles motion. Furthermore, the screened interaction energy between two comoving ions shows oscillations as a function of the interionic separation that may give rise to a wake-riding bound state of the ions, whereas the total energy loss of those ions shows both constructive and destructive interference effects in comparison with the energy loss of independent ions. In the case of static coadsorption on doped graphene, strong screening of the ion-ion electrostatic interaction energy is found as a function of their separation, whereas antiscreening is found in the interaction energy between two dipoles having dipole moments perpendicular to graphene. In addition, shallow minima are found in the interaction energies at finite separations between two ions and between two dipoles having dipole moments parallel to graphene due to Friedel oscillations, which are shown to be much weaker than in the case of coadsorption on a comparable two-dimensional electron gas with single parabolic energy band. It is shown that the interaction of graphene with all the above model systems may be effectively controlled by changing the doping density of graphene.