Electronic band properties and superconductivity in La-Ba-Cu-O and Ba-Y-Cu-O

An important step identifies the mechanism responsible for the high-temperature superconductivity in the La-Ba-Cu-O and Ba-Y-Cu-O systems provided by a thorough understanding of their electronic properties. Accordingly, electronic-structure calculations are carried out on the high-T/sub c/ cuprates La/sub 2-y/(Ba,Sr)/sub y/ CuO/sub 4/ and Ba/sub 2/YCu/sub 3/O/sub 7/ with the use of the linear augmented-plane-wave (LAPW) method. The results exhibit many novel features found in previous calculations on the BaPb/sub 1-x/Bi/sub x/O/sub 3/ alloy system, including significant O(2p) orbital character at E/sub F/, half-filled δ-antibonding bands, Fermi-surface nesting, incipient charge-density-wave (CDW) instabilities, low carrier densities, low density of states at E/sub F/, etc. These similarities suggest a common (electron-phonon) mechanism for explaining superconductivity in this class of metallic oxides, one in which the enhanced T/sub c/'s are due to the strong interaction between the conduction-band states near E/sub F/ and the high-frequency O bond-stretching phonon modes