title: Electron-phonon interactions of Si100 and Ge100 superconductors with Ba atoms inside.
abstract: The absolute density of states of isostructural Ba24Si100 and Ba24Ge100 near the Fermi level, which is very relevant for discussion on phonon-mediated superconductivity, is quantitatively evaluated to be 0.28  states  eV⁻¹/Ge  atom and 0.18  states  eV⁻¹/Si   atom by combining soft x-ray photoelectron spectroscopy and magnetic susceptibility measurements. The energetics of the anharmonic motions of the endohedral Ba atoms are also discussed on the basis of the 4d-core-level spectra. The discussion based on these important physical parameters concludes that the unique electron-phonon interactions do not occur due to the local Jahn-Teller distortion of the fragile open cage structure in the phonon-mediated BCS formalism. Compounds with a rigid cage would be essential to give rise to anticipated unique interactions as a key ingredient favored for superconducting paring.
authors.affiliation: Department of Physics, Tohoku University, Sendai, Japan. tangjun@sspns.phys.tohoku.ac.jp
authors.forename: Jun
authors.initials: J
authors.lastname: Tang
authors.forename: Jingtao
authors.initials: J
authors.lastname: Xu
authors.forename: Satoshi
authors.initials: S
authors.lastname: Heguri
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fukuoka
authors.forename: Syoji
authors.initials: S
authors.lastname: Yamanaka
authors.forename: Koji
authors.initials: K
authors.lastname: Akai
authors.forename: Katsumi
authors.initials: K
authors.lastname: Tanigaki