Electronic properties of high-temperature superconductors
The author has developed a semiempirical tight-binding model for the electronic energy bands, the local and total densities of states, and the atomic valences in the high-temperature superconductors La{sub 1.85}Sr{sub 0.15} CuO{sub 4}, YBa{sub 2}Cu{sub 3}O{sub 7}, Br{sub 2}Sr{sub 2}CuO{sub 6}, Bi{sub 2}CaSr{sub 2}Cu{sub 2}O{sub 8}, Tl{sub 2}Ba{sub 2}CuO{sub 6}, Tl{sub 2}CaBa{sub 2}Cu{sub 2}O{sub 8}, Tl{sub 2}Ca{sub 2}Ba{sub 2}Cu{sub 3}O{sub 10}, TlCa{sub 3}Ba{sub 2}Cu{sub 4}O{sub 1}, BaPb{sub 0.75} Bi{sub 0.25}O{sub 8}, and Ba{sub 0.6}K{sub 0.4}BiO{sub 3}. A single tight-binding model, with fully transferable parameters, provides a good description of the electronic structures of all these materials. Calculations of the changes in electronic properties associated with atomic substitutions in YBa{sub 2}Cu{sub 3}O{sub 7}, Bi{sub 2}CaSr{sub 2}Cu{sub 2}O{sub 8}, Tl{sub 2}CaBa{sub 2} Cu{sub 2}O{sub 8}, give results in agreement with expected chemical trends and consistent with observed changes in the superconducting properties. Oxygen vacancies in both La{sub 1.85}Sr{sub 0.15}CuO{sub 4-y} and YBa{sub 2}Cu{sub 3}O{sub 7-y} act as electron donors. This is consistent with the observations that oxygen vacancies degrade the superconductivity and metallic conductivity in these materials. Lanthanum vacancies in La{sub 2-x}CuO{sub 4} donate holes, giving the same electronic effect as doping with divalent metal atoms or excess oxygen in initially stoichiometric La{sub 2}CuO{sub 4}. The author proposes a specific excitonic mechanism for high-temperature superconductivity, which requires insulating metal-oxide layers adjacent to the superconducting planes.
- Research Organization:
- Texas A and M Univ., College Station, TX (USA)
- OSTI ID:
- 5962972
- Country of Publication:
- United States
- Language:
- English
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360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
BISMUTH COMPOUNDS
BISMUTH OXIDES
BROMINE COMPOUNDS
BROMINE OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRONIC STRUCTURE
EXCITONS
HALOGEN COMPOUNDS
HIGH-TC SUPERCONDUCTORS
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
LEAD COMPOUNDS
LEAD OXIDES
MAGNETIC PROPERTIES
MATHEMATICAL MODELS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POINT DEFECTS
POTASSIUM COMPOUNDS
POTASSIUM OXIDES
QUASI PARTICLES
RARE EARTH COMPOUNDS
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SUPERCONDUCTIVITY
SUPERCONDUCTORS
THALLIUM COMPOUNDS
THALLIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
VACANCIES
YTTRIUM COMPOUNDS
YTTRIUM OXIDES