Many-body effects in the electronic structures of alkali-metal-doped C60

We study the electronic structure of alkali-metal-doped C 60 , A x C 60 where A is an alkali metal. To calculate the spectral densities, we apply the dynamical mean-field theory by using the exact diagonalization method. We show that the charge fluctuation occurs in A 3 C 60 due to the competition between the electron-electron and electron-phonon interactions and therefore this material remains metallic, while A 2 C 60 and A 4 C 60 are insulating due to the cooperation between these interactions. Furthermore, we find that there exists a satellite produced by the charge fluctuation at about 1.3 eV below the Fermi level in the spectral densities for A 3 C 60 . We point out that this satellite has been observed as a shoulder in experimental photoemission spectra.