Thermal conduction in glasses and polymers at low temperatures

Phonon scattering in amorphous solids due to anharmonic forces and structural disorder has been investigated. It is found that although anharmonic scattering persists to lower temperatures, when compared with crystalline solids, it is much too weak to affect the low-temperature thermal conductivity. Elastic scattering due to structural disorder can, however, strongly influence the low-temperature conductivity and the experimental results are interpreted in terms of a long correlation length (a approximately 1000 AA) for the correlation in fluctuations of the properties of the solid point to point. There is evidence for values of a of this order from light scattering experiments in many glassy solids.