Abstract
We investigate the temperature dependence of heat conductivity in a one-dimensional chain of atoms with low concentration of defects. Two types of impurities are discussed in detail and compared: (a) the internal degree of freedom of the isolated impurity acts as a harmonic oscillator, and (b) the impurity can be visualised as a two-level system. For the isolated impurity we assume the conventional form of the interaction mechanism which leads to the exact connection between the phonon T-matrix and the impurity Green function (IGF). The latter quantity is calculated within the Mori continued-fraction method and two different strategies, the weak- and the strong-coupling one, are adopted and compared. From the IGF we deduce the respective phonon relaxation times for the heat conductivity formula. It is found that the temperature dependence of heat conductivity displays a flat region (‘plateau’), which is discussed for both types of impurities and for various model parameters.
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