LOCALIZATION OF VIBRATIONAL-MODES IN A LAYERED LATTICE WITH DIAGONAL AND OFF-DIAGONAL DISORDER

This paper discusses the possibility of weak localization of the phono n modes in a nonideal harmonic crystal lattice whose separate layers a re weakly coupled to each other. An expression is obtained for the dif fusivity tenser. The role of inverse coherent scattering processes is studied. It is established that, when such processes occur under condi tions of strong diagonal disorder in the region of relatively low freq uencies, where the dispersion law of the phonon modes exhibits two-dim ensional properties, substantial renormalization of the diffusivity ca n take place. The paper analyzes the situation that occurs under condi tions of off-diagonal disorder when resonant-scattering impurity cente rs are present in the lattice. The question of the possible nature of the low-temperature plateau in the thermal conductivity of the complex crystals BSCCO and BSYCO is discussed. (C) 1998 American Institute of Physics. [S1063-7761(98)01203-7].