QUASI-2-DIMENSIONAL BEHAVIOR OF PHONON SUBSYSTEMS AND THE SUPERCONDUCTIVITY MECHANISM IN PEROVSKITE-LIKE COMPOUNDS

The results of group-theory analysis, lattice dynamical calculations, and experimental data on the vibrational spectra of perovskitelike sup erconductors have been considered together. The layer description of p honon subsystems in these materials has been shown to be valid. The qu asi-two-dimensional nature of the phonon subsystems has been establish ed. The genesis of the bulk modes has been studied. It has been shown that optical vibrations in these crystals can be divided into 3(N(L) - 1) interlayer and 3(N(A) - N(L)) intralayer modes where N(L) and N(A) are the numbers of layers and atoms per primitive unit cell, respecti vely. The interlayer bulk vibrations originate from acoustic layer mod es whereas the intralayer modes are induced by optical vibrations of i solated layers. A sandwich conception of the high-T(c) superconductivi ty mechanism is discussed based on the different roles of different la yers.