Low-energy collective electronic excitations inLiC6,SrC6, andBaC6

Abstract

We present a first-principles study of the electronic band structure and low-energy dielectric response properties of a representative group of graphite intercalated compounds-LiC 6 , SrC 6 , and BaC 6 . Our results obtained from time-dependent density functional theory calculations reveal the presence of different plasmons in these compounds at energies below 12 eV. The presence of these collective electronic excitations is discussed in terms of intra-and interband transitions. In addition to the bulk plasmon, we find the π -and intraband plasmons. However, their properties vary greatly from one material to another. In LiC 6 and BaC 6 , the π plasmon is a two-dimensional excitation, whereas in SrC 6 it has a three-dimensional character. As for the intraband plasmon, it is observed in all momentum-transfer symmetry directions, with rather strong anisotropy in the energy position between momentum transfers in the basal carbon plane and perpendicular to it. Also, we discuss the appearance in SrC 6 and BaC 6 of a low-energy collective electronic mode with the characteristic soundlike dispersion in terms of the energy bands crossing the Fermi level with different group velocities. We find a correlation between the appearance of such low-energy electronic modes and the occupation of the graphite interlayer band.

Multispectral graphene-based electro-optical surfaces with reversible tunability from visible to microwave wavelengths

“…Our results show that the Fermi energy of MLG can be reversibly increased up to 1.5 eV which is consistent with the band structure calculations of LiC 6 . 30 Raman analysis also shows that the graphene layer stays intact even after 20000 intercalation/deintercalation cycles suggesting that the degradation of the devices is not due to structural damages to the graphene layer but instead due to the loss of Li-ions on the cathode electrode ( Figure S19 ).…”

Surface plasmons on Pd(110): An ab initio calculation

“…In order to eliminate such broadening, we use an equivalent formulation where, first, the imaginary part of χ o GG is evaluated as described, e.g., in Ref. [72]. Subsequently, Re[χ o GG ] is calculated via the Kramers-Kronig relation.…”