A Calculation of Electronic States in YBa_2Cu_3O_y

概要

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To clarify the optical properties of the oxide superconductors with the Cu-O plane and chain, one-electron energy levels and transition energies of a (CuO_5)^<8-> cluster and a (CuO_2)^<3-> cluster in YBa_2Cu_3O_<6.0> are calculated using the unrestricted SCF-X_α SW method. In the (CuO_5)^<8-> cluster, the observed optical transitions at 1.7 eV, 1.8 eV, 2.4 eV, 3.0 eV and 4.1 eV are assigned to the charge transfer (CT) transitions from O 2p to Cu3d_<x^2-y^2> and to the d-d transition from Cu 3d_<xz>+3d_<yz> to 3d_<x^2-y^2>. In the (CuO_2)^<3-> cluster, the observed optical transitions at 4.1 eV and 4.5 eV are assigned to the internal transition from Cu 3d_<z^2> to Cu 4p and to the CT transition from O 2p to Cu 4s, respectively. In addition, from the calculation on a hole-doped (CuO_5)^<7-> cluster in the YBa_2Cu_3O_<6.8>, it is found that the transitions observed in the low-energy region may be assigned to the charge transfer transitions from O 2p to Cu 3d_<z^2>, and to the d-d transition from Cu 3d_<xz>+3d_<yz> to 3d_<z^2>.
社団法人応用物理学会の論文
1992-03-15