A generalization of the Drude model is studied. On the one hand, the free motion of the particles is allowed to be sub- or superdiffusive; on the other hand, the distribution of the time delay between collisions is allowed to have a long tail and even a nonvanishing first moment. The collision averaged motion is either regular diffusive or Lévy-flight-like. The anomalous diffusion coefficients show complex scaling laws. The conductivity can be calculated in the diffusive regime. The model is of interest for the phenomenological study of electronic transport in quasicrystals.

• Received 18 November 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.2176