Transfer-Integral Expansion for the d-p Model of the CuO_2 Plane : Ground State of the Undoped System

概要

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The d-p model of the CuO_2 plane is studied by means of the perturbation theory. Our Hamiltonian consists of the full energy terms, i.e., the transfer terms t_<dp> between Cu d and O p orbitals, t_<pp> between the p orbitals, and the on-site (U_d, U_p) and intersite (V) Coulomb interactions. The energy of the ground state of the undoped charge-transfer-type insulator, E_g, is expanded in powers of the transfer terms up to their fifth order. The obtained perturbation correction to E_g consists of terms of (t_<dp>)^<2n>(t_<pp>)^<n'> with integers n(≥1) and n'(≥0). The superexchange interaction J is found to be affected considerably by the presence of t_<pp>. The role of V in the stability of the charge-transfer-type ground state is also clarified. In the light of the obtained results, the ground state of La_2CuO_4 is discussed by use of the realistic parameter values given by Hybertsen et al.
社団法人日本物理学会の論文
1993-01-15