Coulomb screening effects on the optoelectronic far-infrared properties of spatially separated few-layer graphene

• The optical transitions in layer structures with isolated mono- or bilayer graphene.
• The positions of the transition turning points can be tuned.
• The system and structure parameters can be determined from the optical conductivity.
• One observed peak in the infrared region with the interlayer screened effect.

We investigate the longitudinal optical conductivity of spatially separated few-layer graphene analytically and numerically. Each layer could be monolayer or bilayer graphene. The density–density correlation function has been screened by the dielectric function using the random phase approximation, which includes the inter-layer Coulomb coupling. In the presence of the potential function between the layers, the carrier densities in each layer can be tuned respectively. In these two-dimensional layered structures, the main contributions to the optical conductivity are from the intra- and inter-band transition channels in a same layer. In the infrared region, the Drude optical conductivity was observed by the unscreened intra-band transition process. But in the presence of the inter-layer Coulomb interaction, one peak structure of the optical conductivity is observed which can be modified by the dielectric environment. From the number of turning points and the turning positions, the carrier density, the Fermi wavevector, and the layered structure can be determined.