High-resolution angle-resolved photoemission studies of quasiparticle dynamics in graphite

Abstract

We obtained the spectral function of the graphite $H$ point using high-resolution angle-resolved photoelectron spectroscopy (ARPES). The extracted width of the spectral function (inverse of the photohole lifetime) near the $H$ point is approximately proportional to the energy as expected from the linearly increasing density of states (DOS) near the Fermi energy. This is well accounted for by our electron-phonon coupling theory considering the peculiar electronic DOS near the Fermi level. We also investigated the temperature dependence of the peak widths both experimentally and theoretically. The upper bound for the electron-phonon coupling parameter is 0.23, nearly the same value as previously reported at the $K$ point. Our analysis of temperature-dependent ARPES data at $K$ shows that the energy of a phonon mode of graphite has a much higher energy scale than 125 K, which is dominant in electron-phonon coupling.