Coherent view on fullerenes: phonon-mediated correlated superconductivity and unusual normal state optical conductivity

The wide range of experimental observations on fullerene superconductors ca n be understood if the Coulomb repulsion is included in addition to the ele ctron-phonon interaction in the pairing kernel. These are characterized by lambda approximate to 0.7-0.8 and VCNF approximate to 0.3-0.4, where lambda is the dimensionless electron-phonon coupling constant, V-C the screened C oulomb repulsion, and N-F is the density of states at the Fermi level. This view of phonon-mediated correlated superconductivity is applied to the nor mal state fullerenes to check if an unusual feature observed in the normal state can also be understood within the view: the suppressed Drude weight a nd concomitant mid-infrared (MIR) peak in the optical conductivity. The Dru de weight in the calculated optical conductivity is strongly suppressed., b eing similar to0.4 of the total intraband spectral weight, and is transferr ed to the MIR region around and above 0.06 eV which is somewhat less pronou nced and much broader compared with the experimental observation by DeGiorg i et al. (C) 2001 Elsevier Science B.V. All rights reserved.