Graphene Conductivity and Dielectric Response at THz frequencies

The calculations of the dynamical conductivity of graphene allows further determination of the high frequency, from dc to optical frequencies, response of the real and imaginary parts of the dielectric constant of graphene. In this study we explore how the dynamical conductivity, dielectric properties and refractive index of single layer graphene vary as a function of frequency for different carrier concentrations and scattering times. We play particular attention to the differing roles of the intra- and interband transitions and explore the THz response of graphene as a possible functional material to bridge the so-called THz gap between electronics and optics. We find in the 1-10 THz frequency region that for moderately doped graphene (i) ε₁ is negative and approaches values in the mid -10⁵ but does not vary strongly at lower frequencies and (ii) ε₂ is positive for all THz frequencies explored but is one to two orders lower in magnitude; comparisons are made with noble metals. We also calculate the variation of real and imaginary components of the refractive index with wavelength. Potential applications in graphene based antennas and metamaterials are discussed.