Breakdown of the rigid-band picture in alkali-metal-doped C60: A2C60 and A4C60

The origin of the breakdown of the rigid-band picture in alkali-metal-doped C60, AχC60 (AK, Rb, etc.), is investigated by using a model fully based on the results of first-principle calculations. We find that both the electron-electron and the electron-phonon interaction play important roles to the electronic states of A2C60 and A4C60.