Phonons in superconducting CaC6 studied via inelastic x-ray scattering

We investigate the dispersion and temperature dependence of a number of phonons in the recently discovered superconductor CaC(6) utilizing inelastic x-ray scattering. Four [00L] and two ab-plane phonon modes are observed, and measured at temperatures both above and below T(c). In general, our measurements of phonon dispersions are in good agreement with existing theoretical calculations of the phonon dispersion. This is significant in light of several discrepancies between experimental measurements of phonon-derived quantities and theoretical calculations. The present work suggests that the origin of these discrepancies lies in the understanding of the electron-phonon coupling in this material, rather than in the phonons themselves.