paper

Electron-phonon coupling and electron self-energy in electron-doped graphene: calculation of angular resolved photoemission spectra

arXiv:0707.1467 · doi:10.1103/PhysRevB.76.205411

Abstract

We obtain analytical expressions for the electron self-energy and the electron-phonon coupling in electron-doped graphene using electron-phonon matrix elements extracted from density functional theory simulations. From the electron self-energies we calculate angle resolved photoemission spectra. We demonstrate that the measured kink at eV from the Fermi level is actually composed of two features, one at eV due to the twofold degenerate E mode, and a second one at eV due to the A mode. The electron-phonon coupling extracted from the kink observed in ARPES experiments is roughly a factor of 5.5 larger than the calculated one. This disagreement can only be partially reconciled by the inclusion of resolution effects. Indeed we show that a finite resolution increases the apparent electron-phonon coupling by underestimating the renormalization of the electron velocity at energies larger than the kinks positions. The discrepancy between theory and experiments is thus reduced to a factor of 2.2. From the linewidth of the calculated ARPES spectra we obtain the electron relaxation time. A comparison with available experimental data in graphene shows that the electron relaxation time detected in ARPES is almost two orders of magnitudes smaller than what measured by other experimental techniques.

9 pages, 7 figures, see also Matteo Calandra and Francesco Mauri, arXiv:0707.1492

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