POLARON EXCITATIONS IN DOPED C-60 - EFFECTS OF DISORDER

The effects on C60 of thermal fluctuations of phonons, misalignment of C60 molecules in a crystal, and other intercalated impurities (C70, oxygens, and so on) are simulated by disorder potentials. The Su-Schrieffer-Heeger-type electron-phonon model for doped C60 is solved with Gaussian bond disorder and also with site disorder. Sample averaging is performed over a large number of disorder configurations. The distribution of bond lengths and electron densities are shown as functions of the disorder strength and the additional electron number. The stability of polaron excitations as well as dimerization patterns are studied. Polarons and dimerization in lightly doped cases (C60(-1,-2)) are relatively stable against disorder, as is indicated by peak structures in the distribution functions. In more heavily doped cases, several peaks merge into a single peak, showing the breakdown of polaron structures as well as the decrease of the dimerization strength. The possibility of observation of polaronic lattice distortions and electron structures in doped C60 is discussed.