The effects of substrate on electronic and optical properties of triangular and hexagonal graphene nanoflakes with armchair edges are investigated by using a configuration interaction approach beyond double excitation scheme. The quasiparticle correction to the energy gap and exciton binding energy are found to be dominated by the long-range Coulomb interactions and exhibit similar dependence on the dielectric constant of the substrate, which leads to a cancellation of their contributions to the optical gap. As a result, the optical gaps are shown to be insensitive to the dielectric environment and unexpectedly close to the single-particle gaps.
@article{arxiv.1308.4790,
title = {Substrate effects on quasiparticles and excitons in graphene nanoflakes},
author = {W. Sheng and M. Sun and A. Zhou and S. J. Xu},
journal= {arXiv preprint arXiv:1308.4790},
year = {2015}
}