ELECTRONIC-STRUCTURE OF THE 2-LEGGED LADDER COMPOUND LA1-XSRXCUO2.5

The band properties of La1-xSrxCuO2.5, an orthorhombic cuprate that co ntains a pair of nearly orthogonal two-legged ladders and undergoes an insulator-metal transition near x approximate to 0.2, have been calcu lated using the linear augmented-plane-wave method. The undoped x = 0 results feature four half-filled sigma bands that exhibit anisotropic (i.e., v(parallel to)/v(perpendicular to) approximate to 4) rather th an one-dimensional (1D) characteristics near E(F). A tight-binding ana lysis shows that, for ladders in the x-y plane, the sigma bands at E( F) reflect a similar to 50-50 O(2p)-Cu(3d) admixture, with d(x(2) - y( 2)) orbitals dominating (similar to 75%) the 3d fraction, but containi ng sufficient d(yz) - d(3z(3) - r(2)) hybridization (similar to 12%+12 %) to wash out most 1D features via interladder coupling.