Raman Scattering Study of Ba-doped C60 with t1g States

TL;DR

This study investigates the vibrational and electronic properties of Ba-doped C60 fullerides using Raman spectroscopy, revealing insights into electron-phonon interactions, charge transfer, and hybridization effects relevant to superconductivity.

Contribution

It provides a detailed analysis of Ba-doped C60 Raman spectra, quantifies electron-phonon coupling, and discusses charge transfer and hybridization effects for the first time.

Findings

Splitting of Hg modes in Ba4C60 and Ba6C60 at room temperature.

Derived density of states at Fermi energy as 7 eV^-1 for Ba4C60.

Electron-phonon coupling constant λ approximately 1.0.

Abstract

Raman spectra are reported for Ba doped fullerides, BaxC60(x=3,4,and 6). The lowest frequency Hg modes split into five components for Ba4C60 and Ba6C60 even at room temperature, allowing us a quantitative analysis based on the electron-phonon couping theory. For the superconducting Ba4C60, the density of states at the Fermi energy was derived as 7 eV-1, while the total value of electron-phonon coupling \lambda was found to be 1.0, which is comparable to that of K3C60. The tangential Ag(2) mode, which is known as a sensitive probe for the degree of charge transfer on C60 molecule, shows a remarkable shift depending on the Ba concentration, being roughly consistent with the full charge transfer from Ba to C60. An effect of hybridization between Ba and C60 \pi orbitals is also discussed.