Unraveling the acoustic electron-phonon interaction in graphene

Using a first-principles approach we calculate the electron-phonon couplings in graphene for the transverse and longitudinal acoustic phonons. Analytic forms of the coupling matrix elements valid in the long-wavelength limit are found to give an almost quantitative description of the first-principles matrix elements even at shorter wavelengths. Using the analytic forms of the coupling matrix elements, we study the acoustic phonon-limited carrier mobility and quasiparticle lifetime observable in photoemission spectroscopy for temperatures 0-200 K and high carrier densities of 10(12)-10(13) cm(-2). We find that the intrinsic effective acoustic deformation potential of graphene is Xi(eff) = 6.8 eV and that the temperature dependence of the mobility mu similar to T-alpha in the Bloch-Gruneisen regime increases beyond an alpha = 4 dependence even in the absence of screening when the true coupling matrix elements are considered. The alpha > 4 temperature dependence of the mobility is found to originate in a similar temperature dependence of the relaxation time at the Fermi level. The large disagreement between our calculated deformation potential and those extracted from experimental measurements (18-29 eV) indicates that additional or modified acoustic phonon-scattering mechanisms are at play in experimental situations.