Электронно-дырочные димеры в "родительской" фазе квази-2D-купратов

Abstract

One of the most important features of the parent cuprates such as La2CuO4, which predetermines their unusual behavior under non-isovalent substitution, is high ionic polarizability and proximity to the «polarization catastrophe». We show that at the same time parent cuprates are characterized by a charge transfer instability with the formation of a system of metastable dipole-active «Mott-Hubbard» excitons, or electron-hole (EH) dimers. Non-isovalent substitution shifts the phase equilibrium in the direction of condensation of EH-dimers and the formation of an inhomogeneous EH-liquid, in the simplest model, equivalent to a system of composite bosons. To effectively describe the electronic state of doped cuprates, it is proposed to use the S = 1 pseudospin formalism, which allows one to consider novel charge states of the Anderson RVB-type phase. The recombination of EH-dimers under a critically small value of the energy of local and nonlocal correlations leads to the transition of the system to the Fermi-liquid state.