Andersen Group El.-Phon. QMC C60 GW Resistivity saturation


The photoemission spectrum from the t1u band of A3C60 shows an exceptionally large width, being about a factor of five larger than expected from band structure calculations. This may be explained in terms of phonon and plasmon satellites (M. Knupfer et. al, Phys. Rev. B 47, 13944 (1993)). The electron-plasmon coupling has been calculated and found to be rather strong (Phys. Rev. B 48, 7651 (1993))).

Since the t1u band width and the phonon frequencies are comparable, one may expect Migdal's theorem to be violated. The photoemission spectrum has been calculated for a model of A3C60, using a cumulant expansion, which goes beyond Migdal's theorem ( Phys. Rev. B 50, 10462 (1994)). The calculation shows multiple satellites and a new broadening mechanism.

The photoemission spectrum has also been calculated for a free negatively charged C60 molecule, and the comparison with experiment has been used to estimate the electron-phonon interaction from the strengths of the phonon satellites (Phys. Rev. Lett. 47, 1875 (1995)).

Auger and photoemission spectra have been compared for C60, K3C60 and K6C60 to determine U (Phys. Rev. B 48, 18296 (1993)). For C60 and K6C60 it was found that U~1.4-1.5 in agreement with earlier measurements for C60. The analysis for K3C60 is strongly complicated due to intermolecular charge transfer processes during the emission process, but it was concluded that U has a similar magnitude for K3C60 as for C60.

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