Dielectric function and plasmons in grapheneA. Hill, S. A. Mikhailov and K. Ziegler
Institut für Physik, Universität Augsburg - D-86135 Augsburg, Germany, EU
received 12 May 2009; accepted in final form 7 July 2009; published July 2009
published online 4 August 2009
The electromagnetic response of graphene and the spectrum of collective plasmon excitations are studied as a function of wave vector and frequency. Our calculation is based on the tight-binding band structure, including both valleys. As a result, near the Dirac points we find plasmons whose dispersion is similar to that obtained in the single-valley approximation by Dirac fermions with some anisotropy though. In contrast to the calculation for a single Dirac cone, we find a stronger damping of the plasmon modes due to interband absorption. Our calculation also reveals effects due to deviations from the linear Dirac spectrum as we increase the Fermi energy, indicating an anisotropic behavior with respect to the wave vector of the external electromagnetic field.
73.20.Mf - Collective excitations (including excitons, polarons, plasmons and other charge-density excitations).
© EPLA 2009