Dielectric, charge and phase-separation instabilities in pseudospin-electron model of high- T c superconductors

The possible instabilities in high- T _c superconductors as well as their low-frequency dynamics are analyzed within the pseudospin-electron model involving Hubbard-type electron correlations and local anharmonic vibrations. The instabilities with respect to polarization and/or charge fluctuations caused by the effective interactions via conducting electrons are obtained from the temperature dependencies of the dynamic susceptibilities calculated in the generalized random phase approximation. The corresponding changes in the low-energy spectrum are investigated.