Accession Number : ADA253975
Title : Covalent Electron Transfer Theory of Superconductivity
Descriptive Note : Technical rept.
Corporate Author : MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
Personal Author(s) : Dionne, Gerald F
Report Date : 19 Jun 1992
Pagination or Media Count : 170
Abstract : Following a brief review of phenomenological origins, a comprehensive discussion of the physics and chemistry of super- conducting perovskite systems is presented. The covalent transfer theory developed in 1987, which was based on the normal- state electrical behavior of large polarons, is refined to include a molecular-orbital analysis of the electron transfer probability (assumed to be unity in the original model). An examination of the local magnetic superexchange interactions between Cu2-O2-Cu2+ ions indicates that preconditions for the onset of superconduction include a breakdown in static antiferromagnetic order to eliminate the exchange contribution to the polaron trap energy. The occurrence of magnetic frustration is explained by the existence of mobile polaron ions in zero-spin states. By comparing the covalent transfer and electron hopping mechanisms, a new two-fluid function is derived for the temperature-dependent distribution of normal and superelectrons. From the population of carriers that are not thermally activated (hopping), condensation to the superconducting state occurs in the form of dynamic ferroelectric chains of ordered dipoles, with the condensation energy directly proportional to the square of the supercarrier population. With this relation, it is then possible to derive direct expressions between the measurable superconduction parameters and the effective supercarrier density as functions of temperature. Based on these concepts, computed values of critical temperature, magnetic field, and current density, as well as specific heat, penetration depth, coherence length, and microwave surface resistance all compare favorably with measured values, both in magnitude and as functions of temperature.
Descriptors : *ELECTRON TRANSFER , *SUPERCONDUCTIVITY , FUNCTIONS , IONS , METALS , CATIONS , DENSITY , TEMPERATURE , MAGNETIC FIELDS , MODELS , INTERACTIONS , DYNAMICS , HIGH TEMPERATURE , RESISTANCE , SUPERCONDUCTORS , THEORY , PROBABILITY , ENERGY , COHERENCE , FERROELECTRICITY , MOLECULAR ORBITALS , CONDENSATION , SPIN STATES , SPECIFIC HEAT , STATICS , CURRENT DENSITY , MICROWAVES , CRITICAL TEMPERATURE , SURFACES , CHEMISTRY , ELECTRONS , PENETRATION , PHYSICS , LENGTH , DIPOLES
Subject Categories : Electrical and Electronic Equipment
Distribution Statement : APPROVED FOR PUBLIC RELEASE