PLATEAU IN TEMPERATURE-DEPENDENCE OF THERMAL-CONDUCTIVITY OF GLASSES DUE TO INDIRECT PHONON-PHONON INTERACTION

It is shown that the low lying excitations of glasses, the so called two level systems (TLS), being in a virtual state induce indirect phonon-phonon interactions of a coherent type. These indirect 3-phonon interactions are responsible for the plateau in temperature dependence of thermal conductivity followed by a linear increase in ae at higher temperatures (ae(T) approximately T).