No abstract

The density of states of a U-impurity in a chain of trans-polyacetylene is calculated as a function of the atomic impurity level and the hybridization energy. A residual gap in the density of states of the conduction band is included. It is shown that a Kondo-like resonance exists a t the top of the gap and that a logT behavior should occur in the resistivity of the sample, as experiments have revealed. We demonstrate that in order to observe the resonance, the gap must be smaller than the Kondo temperature in the gapless system.As experimental synthesis has improved, trans-polyacetylene (PA) has acquired a room temperature conductivity rivaling that of copper [ 1-31. The temperature dependence of the conductivity is far from metallic, however [4]. Activated transport is observed from room 0 Les Editions de Physique

A T-matrix formalism is used to calculate local electric fields around clusters of prolate spheroids in the long-wavelength regime. The calculations are performed as a function of interparticle distance as well as angle of orientation. The observed red shifts in the resonant wavelengths of the characteristic peaks are shown to obey an exponential relationship as a function of interparticle separation and a sinusoidal relationship as a function of angle of rotation of the spheroid. The behavior of the cluster is discussed and the two effects of separation and rotation are compared.

No abstract

No abstract