Theoretical study on the photoemission spectra of A3C60 (A=K and Rb)

We calculate the spectral density for A(3)C(60) based on the dynamical mean-field theory and compare our results with the experimental photoemission spectra. 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 consequently the material remains metallic although both interactions are considerably strong. The charge fluctuation in A(3)C(60) means the resonance between C-60(3-) + C-60(3-) and C-60(2-) + C-60(4-) because these two states have almost the same energy. We find a satellite derived from the charge fluctuation in the spectral density for A(3)C(60). It is pointed out that this satellite corresponds to the shoulder observed only for A(3)C(60). Also, we find that the broadening of the lowest-unoccupied-molecular-orbital-derived band is originated in the multiplet splitting. Thus, our results can successfully explain the experimental photoemisson spectra for K3C60 and Rb3C60.