Electron-phonon Pairing Mechanism for Superconductivity in K3C60 Fullerides

摘要

The electron pairing mechanism leading to superconducting state in K3C60 fullerenes is explored within the framework of strong coupling theory. The intercage interactions between C60 cages and expansion of lattice due to the intercalation of K atoms are investigated using the nearest neighbor interactions. The renormalized Coulomb repulsive parameter * and the electron phonon coupling strength are obtained for the intermolecular phonon frequency er, keeping in mind that the free electrons in lowest molecular orbital are coupled with intermolecular phonons. Tc is then estimated as 5 K, which is much lower as compared with the reported value. The electrons also couple with the intramolecular phonons then Tc enhances to 22 K. In this approach the carbon isotope effect exponent, the energy gap ratio, effect of pressure and volume on Tc is calculated which support the superconducting state.