Inelastic X-ray Scattering Study of Phonons in Superconducting CaC6

TL;DR

This study uses inelastic x-ray scattering to analyze phonons in the superconductor CaC6, revealing agreement with theory and suggesting discrepancies are due to electron-phonon coupling understanding.

Contribution

First inelastic x-ray scattering investigation of phonons in CaC6, clarifying phonon behavior and electron-phonon interactions in this superconductor.

Findings

Phonon dispersions agree with theoretical calculations.

Discrepancies in previous measurements likely stem from electron-phonon coupling understanding.

Temperature dependence of phonons observed across T_c.

Abstract

We investigate the dispersion and temperature dependence of a number of phonons in the recently discovered superconductor CaC6 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.