Plasmon dispersion in graphite: A comparison of current ab initio methods

Article

关键词: ELECTRON-HOLE EXCITATIONS;    DENSITY-FUNCTIONAL THEORY;    WAVE-VECTOR DEPENDENCE;    OPTICAL-PROPERTIES;    GREENS-FUNCTION;    QUASI-PARTICLE;    BAND-STRUCTURE;    ABSORPTION;    EQUATION;    SPECTRA;   

DOI  :  10.1103/PhysRevB.100.045205

来源: SCIE

【 摘 要 】

We perform a systematic study of the macroscopic dielectric function and electron energy loss (EEL) spectra for graphite. We obtain the dispersion behavior for the n plasmon, as a function of the momentum transfer q for two nonequivalent paths that traverse the first four Brillouin zones. We carry out these calculations within both time-dependent density functional theory (with two exchange-correlation functionals) and the Bethe-Salpeter equation. Additionally, we explore the effects of using the complete excitonic Hamiltonian (with all electron-hole pairs and antipairs), and within the Tamm-Dancoff approximation (neglecting antipairs). By analyzing the behavior of the macroscopic dielectric function, we are able to determine which peaks are predominantly from plasmonic behavior or only interband transitions. We compare the calculated spectra against several experiments that span almost five decades; our results present clear trends that follow the physical origins of the observed peaks. We carry out this study over a large range of momentum transfer in order to better evaluate the different theoretical methods compared to experiment, and predict the plasmonic behavior beyond available experimental data. Our results indicate that including the complete Hamiltonian with the exciton coupling included is essential for accurately describing the observed EEL spectra and plasmon dispersion of graphite, particularly for low values of momentum transfer. However, the solution of the Bethe-Salpeter equation is computationally intensive, so time-dependent density functional theory methods used in conjunction with the complete Hamiltonian may be an attractive alternative.

【 授权许可】

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