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Abstract

We investigate the nature of the electronic ground state and
electron-lattice couplings for doped chains of CuO4 plaquettes or CuO6
octahedra. The undoped configuration implies here Cu 3d(9) and O 2p(6)
formal valence states. The results of multiconfiguration calculations
on 4-plaquette (or 4-octahedra) linear clusters indicate strong
electron-lattice interactions and polaronic behavior of the doped
particles, for both electron and hole doping. For certain phases of the
oxygen-ion half-breathing distortions a multiwell energy landscape is
predicted. Since each well is associated to carriers localized at
different sites, the half-breathing displacements induce charge
transfer along the chain. In the case of hole doping, the trends found
by ab initio multiconfiguration calculations on 4-octahedra clusters
are confirmed by density-matrix renormalization-group calculations for
a p-d, extended Hubbard model with chains of few tens of CuO4
plaquettes. Under the assumption of charge separation and the formation
of 1/3-doped stripes, our results seem to support the traveling
charge-density wave scenario proposed in some recent contributions for
superconductivity in copper oxides.