Universal Behavior of Anomalous Ionic Conductivity : Relaxation Mode Theory : Condensed Matter: Structure, etc.

概要

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On the basis of the relaxation mode theory in a noninteracting lattice gas, the anomalous dynamic conductivity Reσ(ω)=σ(0)+Aω^s+A'ω^s', s≉0.6, s'≉1 is fully examined in a random supercell system having a uniform distribution of the activation energies U_<min> ⪇ U ⪇ U_<max>; the low-frequency and high-temperature region Aω^s is governed by the extended nondiffusive modes, while the high-frequency and low-temperature region A'ω^s' is regulated by the localized nondiffusive modes. The dynamical crossover exists in-between. The frequency power s is almost independent of temperature but s' changes with it. The coefficient approximately given by A ≉ βexp{-β(1 - s)U_<max>} shows a strong temperature dependence since s ≉ 0.6, and A' ≉ βexp{-β(1-s')U_<min>} depends but weakly on temperature because s' ≉ 1. All these characteristics, which are quite consistent with the experiments of Nowick et al., are originated in a single mechanism of the mode diffusion length L_≉ _^</2> and density of states D_≉ _^</2> where _ is the mode relaxation time.
2000-08-15