Interband plasmons in supported graphene on metal substrates: Theory and experiments

Insights on the Excitation Spectrum of Graphene Contacted with a Pt Skin

“…However, even high-performance ab initio calculations that include quasi-particle and excitonic G 0 W 0 -BSE corrections [58], yield the π plasmon peak at about ω p ≈ 4.6 eV, which is still lower than the value observed in Refs. [8,39], but agrees well with other experimental measurements where the π plasmon peak was found in the energy range 4 < ω p < 5 eV [7,55,59,60]. A question arises then as to why is there so large variability among different experimental measurements of the π plasmon peak position in graphene.…”

“…This shortcoming of the empirical method is expected, because using the bulk dielectric function Pt in the local limit is not sufficient to describe the dispersive response of the Pt surface, as can be seen in Figure 4 below. It should be emphasized that the present measurements, as well as other similar measurements of the π plasmon in graphene supported by metallic Pt(111) and Ni(111) surfaces [8,39], systematically find that the π plasmon energy in the optical limit, Q ≈ 0, is more than 1 eV higher than the energy of the π plasmon in unsupported graphene, as predicted by ab initio calculations [34,57]. The reason for this discrepancy may be attributed to the random-phase approximation (RPA), used in these ab initio calculations, which does not include quasi-particle corrections of graphene's π and π * bands and excitonic effects (interaction between excited π * -electron and π-hole).…”

“…The graphene dielectric response in the range of energies around the π plasmon peak will also be described using a two-fluid hydrodynamic model, which was very successful in modeling the EELS in graphene supported by the Pt(111), Ru(0001) and Ni(111) substrates [39]. In this model, the polarizations of graphene's π and σ bands are described by two response functions of the Drude-Lorentz type, given by…”

“…[37,38]. This simple empirical approach is analytically tractable and it was found to be quite effective in describing the EELS data for graphene on various metallic surfaces [39].…”

Growth and electronic structure of graphene on semiconducting Ge(110)

“…This leads to the increase of the graphene-related signal in the EELS spectra as the energy of the electron beam is decreased, which manifests itself as an increase of the intensity in the energy range of 3.5 − 6.5 eV as well as in the increase of the overall background for the energies above 15 eV. The first feature is assigned to the so-called π plasmon [47][48][49], the energy of which is determined as 6.33 ± 0.25 eV by a curve fitting procedure. The second observation is connected to the increase of the intensity of the π + σ plasmon as well as the increase of the background of the low energy inelastically scattered electrons.…”