Theoretical Study on the Superconductivity Induced by the Dynamic Jahn-Teller Effect in Alkali-Metal-Doped C_<b>60</b>

Abstract

We investigate the superconductivity in alkali-metal-doped C 60 , A 3 C 60 . ( A =K, Rb, etc.) To take account of both the electron-electron and electron-phonon interactions, we employ a model introduced in our previous study for explaining the reason why A 2 C 60 and A 4 C 60 are, in contrast to A 3 C 60 , insulators despite that these materials are expected to be good metals. It is found that the superconductivity can also be explained on the same basis that is essential for explaining the anomaly in A 2 C 60 and A 4 C 60 . The origin of the superconductivity in our model is the dynamic Jahn-Teller effect; the attractive interaction between the t 1 u electrons is caused by the dynamic Jahn-Teller effect resulting from the pair transfer interaction originated in the coupling between the t 1 u electrons and the H g intramolecular phonons. The order parameter of the superconductivity is spin-singlet and of the A g symmetry. We also point out that the dynamic Jahn-Teller mechanism revealed here is closely related to the Suhl-Kondo mechanism. The multiplicity of the t 1 u bands is indispensable for both mechanisms.