Electronic properties of high-temperature superconductors. Doctoral thesis

Technical Report · Tue Aug 01 04:00:00 EDT 1989

OSTI ID:6904616

Richert, B A

We have 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(1.85)Sr(0.15)CuO4, YBaCu307, Bi2Sr2CuO6, Bi2CaSr2Cu2O8, Tl2Ba2CuO6, Tl2CaBa2Cu2O8, Tl2Ca2Ba2Cu3O10, TlCa3Ba2Cu4O11, BaPb(0.75)Bi(0.25)O3, and Ba(0.6)K(0.4)BiO3. Calculations of the changes in electronic properties associated with atomic substitutions in YBa2Cu3O7, Bi2CaSr2Cu2O8, and Tl2CaBa2Cu2O8 give results in agreement with expected chemical trends and consistent with observed changes in the superconducting properties. For example, substitution of Lead for Bismuth in BiMCaSr2Cu2O8 increases the concentration of hole carriers within the CuO2 planes. Similarly, doping with Mercury or Pb in TlMCaBa2Cu2O8 also affects the carrier concentration, with Hg creating holes and Pb destroying them. Oxygen vacancies in both La(1.85)Sr(0.15)CuO(4-y) and YBa2Cu3O(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 La2-xCuO4 donate holes, giving the same electronic effect as doping with divalent metal atoms or excess oxygen initially stoichiometric La2CuO4. We propose a specific excitonic mechanism for high-temperature superconductivity, which requires insulating metal-oxide layers adjacent to the superconducting planes.

• Research Organization: Air Force Inst. of Tech., Wright-Patterson AFB, OH (USA)
• OSTI ID: 6904616
• Report Number(s): AD-A-217953/9/XAB; AFIT/CI/CIA--89-099
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
BAND THEORY
BARIUM COMPOUNDS
BARIUM OXIDES
BISMUTH COMPOUNDS
BISMUTH OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
CHARGE CARRIERS
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL DOPING
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRONS
ELEMENTARY PARTICLES
EXCITONS
FERMIONS
HIGH-TC SUPERCONDUCTORS
HOLES
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
LEAD COMPOUNDS
LEAD OXIDES
LEPTONS
MATHEMATICAL MODELS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
QUASI PARTICLES
RARE EARTH COMPOUNDS
REFRACTORY METAL COMPOUNDS
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SUPERCONDUCTIVITY
SUPERCONDUCTORS
TANTALUM COMPOUNDS
TANTALUM OXIDES
TRANSITION ELEMENT COMPOUNDS
VALENCE
YTTRIUM COMPOUNDS
YTTRIUM OXIDES