Substrate effects on quasiparticles and excitons in graphene nanoflakes

TL;DR

This study investigates how substrates influence the electronic and optical properties of graphene nanoflakes, revealing that optical gaps are surprisingly unaffected by dielectric environment due to a cancellation effect.

Contribution

It demonstrates that substrate effects on quasiparticle corrections and exciton binding energies cancel out, making optical gaps insensitive to substrate dielectric properties.

Findings

Optical gaps are nearly independent of substrate dielectric constant.

Quasiparticle correction and exciton binding energy are dominated by Coulomb interactions.

Optical gaps closely match single-particle gaps despite substrate variations.

Abstract

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.