Comparative study of the phonons in non-superconducting BaC6 and superconducting CaC6 using inelastic x-ray scattering

Abstract

The low energy phonons of two different graphite intercalation compounds (GICs) have been measured as a function of temperature using inelastic x-ray scattering (IXS). In the case of the non-superconductor BaC6, the phonons observed are significantly higher (up to 20 %) in energy than those predicted by theory, in contrast to the reasonable agreement found in superconducting CaC6. Additional IXS intensity is observed below 15 meV in both BaC6 and CaC6. It has been previously suggested that this additional inelastic intensity may arise from defect or vacancy modes in these compounds, unpredicted by theory (d'Astuto et al, Phys. Rev. B 81 104519 (2010)). Here it is shown that this additional intensity can arise directly from the large disorder of the available samples. Our results show that future theoretical work is required to understand the relationship between the crystal structure, the phonons and the superconductivity in GICs.

6 pages, 5 figures

References in corpus (10)

• Non-adiabatic Kohn-anomaly in a doped graphene monolayer
• Adiabatic and non-adiabatic phonon dispersion in a Wannier function approach
• Anisotropic Electron-Phonon Coupling and Dynamical Nesting on the Graphene Sheets in CaC6
• Superconductivity in Heavy Alkaline-Earths Intercalated Graphites
• Possibility of superconductivity in graphite intercalated with alkaline earths investigated with density functional theory
• Evidence for gap anisotropy in CaC6 from directional point-contact spectroscopy
• Non-adiabatic phonons within the doped graphene layers of XC${}_6$ compounds
• Phonons and superconductivity in YbC${}_6$ and related compounds
• Phonon dispersion and low energy anomaly in CaC${}_6$
• Neutron scattering study of the high energy graphitic phonons in superconducting CaC${}_6$

Cited by in corpus (6)

• Pressure-induced Superconductivity in CaC2
• Superconductivity in graphite intercalation compounds
• Introduction to High-Resolution Inelastic X-Ray Scattering
• Theoretical Investigation of Two-Dimensional Superconductivity in Intercalated Graphene Layers
• Theory of Superconductivity in Graphite Intercalation Compounds
• Superconductivity in Graphene-Lithium