Analysis of electronic structure and charge density of the high-temperature superconductor YBa/sub 2/Cu/sub 3/O/sub 7/
Self-consistent linearized augmented plane wave (LAPW) method calculations of the band structure, density of states, Fermi surface, Coulomb potential, charge density, core-level shifts, and electron-phonon interaction are presented for Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7/. The calculated Sommerfield parameter ..gamma.. is 4.35 mJ(mole Cu)/sup /minus/1/ K/sup /minus/2/, roughly about a factor of 2 smaller than experimentally deduced values of the enhanced value ..gamma.. = (1 + lambda)..gamma../sub 0/, suggesting that the Fermi surface mass enhancement is of the order of unity. The crystal charge density is best represented by overlapping spherical ionic densities when the Cu and O ions are assigned charges of +1.62 and -1.69, respectively, corresponding to about 0.3 holes per oxygen atom. Core-level energies for the inequivalent atoms differ by as much as 0.45 eV for Cu and 0.7 eV for O, amounts which may be detectable by core-level spectroscopies. These results provide important information on the character and magnitude of ionic contributions to bonding in these materials. Within the rigid muffin-tin approximation, calculated McMillan-Hopfield parameters yield estimates for the electron-phonon strength lambda that appear to be too small to account for the observed T/sub c/. We point out an unusual band of oxygen-derived chain states below, but within 0.1 eV of, the Fermi level.
- Research Organization:
- College of William and Mary, Williamsburg, VA (USA)
- OSTI ID:
- 5928600
- Journal Information:
- J. Superconduct.; (United States), Journal Name: J. Superconduct.; (United States) Vol. 1:1; ISSN JOUSE
- Country of Publication:
- United States
- Language:
- English
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75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
ATOMIC MODELS
BAND THEORY
BARIUM COMPOUNDS
BARIUM OXIDES
BORN APPROXIMATION
CHALCOGENIDES
CHARGE DENSITY
COPPER COMPOUNDS
COPPER OXIDES
COULOMB FIELD
CRYSTAL LATTICES
CRYSTAL MODELS
CRYSTAL STRUCTURE
CRYSTALS
ELECTRIC FIELDS
ELECTRON-PHONON COUPLING
ELECTRONIC STRUCTURE
ENERGY DENSITY
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
FERMI LEVEL
IONIC CRYSTALS
ITERATIVE METHODS
LATTICE PARAMETERS
MATHEMATICAL MODELS
MUFFIN-TIN POTENTIAL
ORTHORHOMBIC LATTICES
OXIDES
OXYGEN COMPOUNDS
POTENTIALS
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES