Fluctuational Superconductivity of Magnetic Systems

ISBN-13: 9783540505617 / Angielski / Miękka / 1990 / 258 str.

Maxim A. Savchenko; Alexei V. Stefanovich; M. A. Savchenko

Opis

This is a monograph on the fluctuational theory of superconductivity. The theory was originally developed by M. A. Savchenko in 1964 in response to the work of B. T. Matthias, the discoverer of superconductive compounds. Further development of the theory led to the prediction of the existence of high-temperature superconductors among magnetic and nonmagnetic compounds of rare-earth metals, ceramics, and polymers. In 1987 this prediction was experimentally verified by the discovery of high-Tc superconducting rare-earth metal oxides by I. Bednorz and K. Muller. To date, this is the only account that explains consistently all the available data. The theory of high-temperature superconductivity is based on the concept of an enhanced electron-phonon interaction which leads to an attraction between electrons forming superconducting pairs. This interaction is due to the exchange spin fluctu- ations (exchange enhancement effect). In compounds in which there is no magnetic ordering except at very low temperatures, such as in rare-earth metal oxides, the electron-phonon interaction is strengthened due to fluctuations in the spins of the conducting electrons. If there is magnetic ordering in a superconductor at a tempera- ture higher than or of the same order as the critical superconducting temperature Tc, then the attraction in the electron pairs will be further increased because the Coulomb repulsion is overwhelmed by fluctuations in the spins forming the long-range anti fer- romagnetic order.

Spis treści

1. Introduction.- 2. Exchange Enhancement Effect During Phase Transitions in Magnetically Ordered Crystals.- 2.1 Phase Transition in a Ferromagnet with Quadrupole Interaction.- 2.2 Phase Transition in an Antiferromagnet in a Strong Magnetic Field.- 2.3 Fluctuations and Spin Waves in Ferroelectro-antiferromagnets in a Strong Magnetic Field.- 2.4 Phase Transition in a Crystal with Dislocations in a Strong Magnetic Field.- 3. Phase Lamination and the Exchange Enhancement Effect.- 3.1 Phase Transitions in Complex Magnetic Structures and the Exchange Enhancement Effect in Spin-Orbit Interaction.- 3.2 Phase Diagrams of Complex Magnetic Structures: Phase Lamination.- 3.3 Phase Transitions in Ferroelectro-antiferromagnets.- 4. Superconducting Phases in Rare-Earth Metal Compounds: Phenomenological Theory.- 4.1 Superconducting Compounds of Rare-Earth Metals: Formulation of the Problem.- 4.2 Fluctuation Free Energy: Renormalization Group Equations.- 4.3 Phase Diagram of the Superconducting Compounds of Rare-Earth Metals.- 4.4 Topological Analysis of the Phase Diagram of Superconducting Compounds of Rare-Earth Metals.- 5. Theory of High-Temperature Superconducting Phases in Rare-Earth Metal Compounds.- 5.1 Lagrangian of the System near the Point of Phase Transition to Superconducting State.- 5.2 Electron-Phonon Interaction Parameter for the High-Temperature Superconducting Phase.- 6. Solitons in the Theory of Superconductivity of Magnetic Systems.- 6.1 Generalized Order Parameter in Magnetic Superconductors: Equations for the Superconducting Phase.- 6.2 Soliton Mechanism for Emergence of Superconductivity Accompanying a Phase Transition from Superconducting to Paramagnetic States.- 6.3 Solitons in an Inhomogeneous Superconducting State and Topology.- 6.4 Solitons in the Phase of Coexistence of Superconductivity and Magnetism.- 7. Spin Glasses Based on Rare-Earth Metal Compounds.- 7.1 Phase Transitions in Heavy Rare-Earth Metals.- 7.2 Modern Spin Glass Models.- 7.3 Peculiarities of Vector Fields in Heavy Rare-Earth Metals.- 7.4 Magnetic Susceptibility in the New Spin Glasses.- 7.5 Superconducting Phases in Spin Glasses.- 7.6 Peculiarities of Spin-Wave Dynamics in Spin Glasses.- 8. High-Temperature Superconducting Ceramics.- 8.1 High-Temperature Superconducting Oxides.- 8.2 Spectrum of Quasi-Particles Exchanged by Electrons in HTS Ceramics.- 8.3 Possibility of Increasing the Critical Temperature: Properties of High-Temperature Superconductors.- 9. Theory of High-Temperature Superconductivity of Ceramic Systems.- 9.1 Microscopic Equations for the Superconducting Phase.- 9.2 Separation of Many-Particle Averages in the Superconducting Phase Equations: Wick’s Theorem.- 9.3 Electron-Phonon Interaction in Superconducting Phases: Superconducting Transition Temperature.- 9.4 Phase Lamination in Superconducting States.- 9.5 Microscopic Equations near the Phase Transition Point: Relation to the Phenomenological Theory.- 10. Theory of High-Temperature Superconductivity of Polymer Systems.- 10.1 Quasi-One-Dimensional Organic Superconductors: Polyacetylene as a Possible Superconductor.- 10.2 Criterion for the Emergence of Superconductivity in Polyacetylene.- 10.3 High-Frequency Properties of Polyacetylene in the Nonsuperconducting State.- References.