Charge fluctuation in A(3)C(60) (A=K and Rb): Competition between electron-electron and electron-phonon interactions

We show that charge fluctuation occurs in A(3)C(60) due to the competition between electron-electron and electron-phonon interactions and consequently the material remains metallic although both interactions are considerably strong. We calculate the spectral density for A(3)C(60) based on the dynami cal mean-field theory by using the exact diagonalization method. We find a satellite, which is a direct consequence of the charge fluctuation, at abou t 1.3 eV below the Fermi level. We point out that high-resolution photoemis sion experiments have shown the existence of this satellite.