Year: 2011
Type: article
Abstract: In order to interpret the recent experimental discovery of superconductivity (Tc = 38 K) in Cs3C60 with the A15 structure under pressure, the mechanism of phonon-mediated electron-electron coupling is reconsidered for fullerene superconductors. A primary concern is whether or not Cs3C60 can be understood in a unified picture including previously studied alkali-metal-doped fullerene superconductors, i.e., fcc A3C60 (A = K, Rb, etc.). By extending the Appel-Kohn integral equation in the site representation formalism, the effect of three types (acoustic Ia, optical Io and intramolecular high-frequency IH) of phonons on Tc are analyzed for both fcc and A15 symmetries. The essential point is that the optical phonon mode by which alkali-metal ions at tetrahedral sites couple with electrons holds the key to adjusting whether superconductivity is promoted or prevented. Following the present approach, the following previously unexplained unusual properties are explained naturally for C60-based superconductors: (i) large Coulomb repulsion, (ii) the small isotope effect on Tc and (iii) two types of isotope shift affecting Tc upon different methods of partial substitution. Hence, the stage is set for understanding A15-type fullerene superconductors by applying the same equation as that for fcc-type fullerene superconductors regardless of their structure.
Source: Progress of Theoretical Physics
DOI: 10.1143/ptp.125.1021
Author: Eiko Matsushita
Institution: Gifu University
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: bronze
Awards: G7879866177, G8546646505
OpenAlex ID: W2001786580