Non-adiabatic phonons within the doped graphene layers of XC${}_6$ compounds

Abstract

We report the first Raman scattering measurements of BaC${}_6$, SrC${}_6$, and YbC${}_6$, which along with new data on CaC${}_6$, permits a systematic study of the phonons and the electron-phonon interaction within the doped graphene layers of these compounds. The out-of-plane carbon phonon softens as the spacing of the graphene layers is reduced in the series BaC${}_6$, SrC${}_6$, YbC${}_6$, and CaC${}_6$. This is due to increasing charge in the ${\pi }^{\ast }$ electronic band. Electron-phonon interaction effects between the in-plane carbon modes at $\approx 1500$\invcm and the ${\pi }^{\ast }$ electrons cause a strong non-adiabatic renormalization. As charge is transferred into the ${\pi }^{\ast }$ band these non-adiabatic effects are found to increase concurrent with a reduction in the phonon lifetime.

5 pages, 3 figures, published version

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Cited by in corpus (12)

• Adiabatic and non-adiabatic phonon dispersion in a Wannier function approach
• Superconductivity in Ca-doped graphene
• Phonons in potassium doped graphene: the effects of electron-phonon interactions, dimensionality and ad-atom ordering
• Electronic structure of superconducting KC${}_8$ and non-superconducting LiC${}_6$ graphite intercalation compounds: Evidence for a graphene-sheet-driven superconducting state
• Superconductivity in graphite intercalation compounds
• Raman response of Stage-1 graphite intercalation compounds revisited
• Exact factorization-based density functional theory of electron-phonon systems
• Comparative study of the phonons in non-superconducting BaC6 and superconducting CaC6 using inelastic x-ray scattering
• Non-adiabatic effects in the phonon dispersion of Mg 1--x Al x B 2
• Phonons and superconductivity in YbC${}_6$ and related compounds
• Neutron scattering study of the high energy graphitic phonons in superconducting CaC${}_6$
• The phonon-mediated superconductivity in bismuthates by non-adiabatic pairing