Optical response of coronene in the presence of a metallic substrate

Theoretical research on graphene quantum dots (GQDs) driven by the near-field enhancement on metallic substrates has interest in the practical realm. Here, the GQD is modeled as coronene (a polycyclic aromatic hydrocarbon) with its edges saturated by hydrogen atoms. A combined density functional theory, QED, and statistical formalism has been used to determine the molecular dynamics quantities, such as energy levels and transition dipole moments, and a three-level model for the coronene molecule is obtained. Furthermore, we have characterized the effects of the substrate on the molecule through the enhancement factor (or equivalently, the spectral density function), which can be decomposed into a superposition of various contributions, such as surface waves (SWs) and the quasistatic near field, also known as lossy surface waves. Both of these contributions can be excited by molecular emission in the vicinity of the substrate. Using the three-level model and the substrate enhancement factor, we obtained the population dynamics of the excited levels of coronene placed in the vicinity of the substrate, as well as the modified photonic spectrum.