Electronic structure and magnetic coupling in copper oxide superconductors

Journal Article · Sun Nov 01 00:00:00 EST 1992 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.46.11935· OSTI ID:7197993

Wang, Y J ^[1]; Newton, M D ^[2]; Davenport, J W ^[3]

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1. Department of Physics, State University of New York at Stony Brook, Stony Brook, New York 11794 (United States)
2. Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973 (United States)
3. Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 (United States)

The electronic structure and magnetic coupling in La{sub 2}CuO{sub 4} and Nd{sub 2}CuO{sub 4} have been analyzed using the results of all-valence-electron calculations for (Cu{sub 2}O{sub 11}){sup 18{minus}}, (Cu{sub 4}O{sub 12}){sup 16{minus}}, and (Cu{sub 4}O{sub 20}){sup 32{minus}} clusters, and their {ital p}- and {ital n}-doped variants, embedded in a Madelung potential to represent the crystal environment. The calculations employ the semiempirical incomplete neglect of differential overlap (INDO) method, which is parametrized on the basis of atomic and molecular spectroscopic data, but which makes use of no data from copper oxide materials. The energies of the low-lying cluster spin states are fitted to a Heisenberg Hamiltonian and yield values of {ital J} (134 meV for La{sub 2}CuO{sub 4} and 117 meV for Nd{sub 2}CuO{sub 4}) in close agreement with experiment. The evaluation of {ital J} can be compactly represented in terms of the parameters ({ital t}, {ital U}, and {ital V}) of a one-band Hamiltonian that controls resonance among covalent and ionic valence-bond structures. The resonance mixing is achieved by configuration interaction (CI) among valence-band structures defined in terms of localized molecular orbitals (LMO's) obtained from self-consistent field (SCF) INDO calculations. {ital P} doping is found to involve strong hybridization of the 2{ital p}{sigma} orbitals of the in-plane oxygen ions and the 3{ital d}{sub {ital x}}{sup 2}{minus}{ital y}{sup 2} orbitals of the Cu ions, and the resulting holes are predominantly ({similar to}60%) located in the 2{ital p}{sigma} orbitals. The lowest-energy {ital n}-doped cluster states involve addition of electrons to the 4{ital s}/4{ital p} Cu atom manifolds. However, the separation of these states from low-spin (3{ital d}{sup 10}) alternatives is uncertain because of apparent sensitivity to the representation of the crystal potential, as found by Martin.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 7197993
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 46:18; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
HIGH-TC SUPERCONDUCTORS
ELECTRONIC STRUCTURE
MAGNETIC PROPERTIES
CONFIGURATION INTERACTION
COPPER OXIDES
COUPLING
CRYSTAL DOPING
LANTHANUM OXIDES
NEODYMIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
LANTHANUM COMPOUNDS
NEODYMIUM COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
665411* - Basic Superconductivity Studies- (1992-)