Theory of the pseudogap in the elementary excitation spectrum of the normal phase of bilayer cuprates

Abstract

Solutions of the integral equations for the pseudogap in the elementary excitation spectrum of current carriers in bilayer cuprates are found. In the general case, the pseudogap possesses s + id symmetry, where the s component is determined by the interaction of holes via the phonon field and the d component is due to the superexchange interaction of the copper spins and the Coulomb-repulsion screened holes. The s and d components exhibit different temperature dependences. This fact enabled us to explain the characteristic features of the temperature behavior of the normal-phase spin susceptibility of lightly doped cuprates, specifically, for the compound YBa₂Cu₄O₈ in the entire temperature interval T>T_c. The wave-number dependence of the pseudogap agrees with the photoemission data for Bi₂Sr₂CaCu₂O_8+y.