Ab initio calculation of the G peak intensity of graphene: Combined study of the laser and Fermi energy dependence and importance of quantum interference effects

We present the results of a diagrammatic, fully ab initio calculation of the $G$ peak intensity of graphene. The flexibility and generality of our approach enables us to go beyond the previous analytical calculations in the low-energy regime. We study the laser and Fermi energy dependence of the $G$ peak intensity and analyze the contributions from resonant and non-resonant electronic transitions. In particular, we explicitly demonstrate the importance of quantum interference and non-resonant states for the $G$ peak process. Our method of analysis and computational concept is completely general and can easily be applied to study other materials as well.