Electronic structure of A4C60: Joint effect of electron correlation and vibronic interactions (original) (raw)

Effects of electron correlation, intrasite vibronic interaction, and merohedral disorder on the electronic structure of K 4 C 60 are investigated with a model approach taking into account all essential interactions in the lowest unoccupied molecular orbital ͑LUMO͒ band. The self-energy was calculated within the GW approximation with self-consistency after the quasiparticle Green function starting from Hartree-Fock band structure. The insulating state arises due to interorbital charge disproportionation within the LUMO band while the band gap is strongly reduced by effects of long-range electron correlation. The results of the calculations are in reasonable agreement with experiment, providing evidence for a Jahn-Teller induced transition from a Mott-Hubbard to a band insulator state. ͓S0163-1829͑99͒51020-5͔