Theoretical phase diagram of unconventional alkali-doped fullerides

By constructing an effective model based on recently calculated ab initio bare interaction parameters, we study the phase diagram of alkali-doped fullerides as a function of temperature and internal pressure. While we use a slave-rotor mean-field theory to determine the metal-insulator-superconductor phase boundaries, we use a variational mean-field approach to detect the magnetic phase transitions. We find a good agreement with experimental phase diagram in both weak and strong coupling limits. We explain the unified description of the phase diagram including the proximity of s-wave superconducting state and the Mott-insulating state, and the existence of Jahn-Teller distorted metallic state using orbital selective physics. We argue that the double electronic occupation of two degenerate orbitals triggers both s-wave superconductivity and Jahn-Teller distortion. While the orbital ordering of two electrons causes the distortion, the remaining single electron in the third orbital causes the metal-insulator transition.