PHASE-SEPARATION AND DIELECTRIC CORRELATIONS IN HTSC

A general description of the phase separation (PS) in HTSC is presented based on a concept of ''soft'' dielectric ordering with respect to the addition of collectivized charge carriers. The possibility of the PS crucially depends on the properties of the PS crucially depends on the properties of the screening ion subsystem. The interaction of electron and ion subsystems determines a large variety of manifestations of the PS under different experimental conditions. It is shown that the assumption of the existence of the PS makes it possible to explain on common grounds a number of experiments on different HTSC, which seem to be quite separate from each other, such as anomalous magnetoresistance at T < T(c) in Ba1-xKxBiO3, the appearance of midgap states in cuprate HTSC, the existence of two plateaus in the dependence of T(c) on composition x in YBa2Cu3O6+x, the appearance of photoinduced superconductivity in yttrium superconductors and others.