High-temperature superconductivity

About: High-temperature superconductivity is a research topic. Over the lifetime, 7263 publications have been published within this topic receiving 175377 citations. The topic is also known as: high-temperature superconductivity.

High-Temperature Superconductivity: Experiment and Theory

Abstract: 1. Introduction.- 1.1 The Discovery of High-Temperature Superconductivity.- 1.2 A New Class of Oxide Superconductors.- 1.3 General Properties of Oxide Superconductors.- 2. Crystal Structure.- 2.1 The Structure of Ba1-xKxBiO3.- 2.2 Lai1-xMxCuO4 Compounds.- 2.2.1 The Structure of La2-xMxCuO4-y.- 2.2.2 A Phenomenological Theory of Structural Phase Transitions in La2CuO4- Based Compounds.- 2.3 Nd2-xCexCuO4 Compounds.- 2.4 Y-Ba-Cu-O-Based Compounds.- 2.4.1 The Structure of YBa2Cu3O7-y.- 2.4.2 Modifications of the YBCO Structure.- 2.5 Bi-Ca-Sr-Cu-O and Tl-Ca-Ba-Cu-O Compounds.- 3. Antiferromagnetism in High-Temperature Superconductors.- 3.1 Antiferromagnetism in La2CuO4 Compounds.- 3.1.1 Magnetic Structure.- 3.1.2 A Phenomenological Theory of Magnetic Phase Transitions in La2CuO4.- 3.1.3 Spin Dynamics in La2?xMxCuO4.- 3.2 Antiferromagnetism in YBa2Cu3O6+x Compounds.- 3.2.1 The Magnetic Phase Diagram.- 3.2.2 Spin Dynamics in YBa2Cu3O6+x.- 3.2.3 Antiferromagnetism of Rare-Earth Ions in REBa2Cu3O6+x.- 3.3 Spin Dynamics Studied by the NMR Method.- 3.3.1 The Knight Shift.- 3.3.2 Spin-Lattice Relaxation.- 4. Thermodynamic Properties of High-Temperature Superconductors.- 4.1 The Anisotropic Ginsburg-Landau Model.- 4.2 Specific Heat.- 4.3 Magnetic Properties.- 5. Electronic Properties of High-Tc Superconductors.- 5.1 Crystal Chemistry of Oxide Superconductors.- 5.2 The Effect of Impurity Substitution.- 5.3 Theoretical Electronic Band-Structure Studies.- 5.3.1 Electronic Band-Structure Calculations.- 5.3.2 Effective Hamiltonians in Models of La2CuO4.- 5.4 Experimental Studies of the Electronic Structure.- 5.4.1 High-Energy Scale Spectroscopy.- 5.4.2 Studies of the Fermi Surface.- 5.4.3 Optical Electron Spectroscopy.- 5.5 Transport Properties.- 5.5.1 Resistivity.- 5.5.2 Hall Effect.- 5.5.3 Thermopower and Heat Conductivity.- 5.6 Superconducting Gap.- 5.6.1 Tunneling Experiments.- 5.6.2 Other Experiments.- 6. Lattice Dynamics and Electron-Phonon Interaction.- 6.1 Phonon Spectra - Neutron Scattering.- 6.2 Optical Investigations.- 6.3 Theoretical Models.- 7. Theoretical Models of High-Temperature Superconductivity.- 7.1 Quasi-Particles in Models with Strong Correlation.- 7.1.1 Model Hamiltonians.- 7.1.2 The One-Hole Quasi-Particle Spectrum.- 7.1.3 Spin Fluctuation Spectrum.- 7.2 Superconductivity in Systems with Strong Correlations.- 7.2.1 Unconventional Ground States.- 7.2.2 Superconductivity in the t-J Model.- 7.2.3 Superconductivity in the p-d Model.- 7.3 Antiferromagnetism and Superconductivity.- 7.4 Electron-Phonon Mechanism.- 7.4.1 Isotope Effect.- 7.4.2 Strong Electron-Phonon Coupling.- 7.4.3 Anharmonic Model of a Superconductor.- 7.4.4 Polarons and Bipolaron Superconductivity.- 7.4.5 Weak Coupling in the Quasi-Two-Dimensional Lattice.- 7.4.6 Spin-Fluctuation and Electron-Phonon Interactions.- 7.5 Exciton Models.- 7.5.1 Plasmon Model.- 7.5.2 Jahn-Teller Excitations and the d-d Model.- 7.5.3 Coulomb Interaction in the Multiband Models.- 8. Conclusion.- References.

Possible high temperature superconductivity in a Ti-doped A?Sc?Fe?As?O (A = Ca, Sr) system

Abstract: We report a systematic study on the effect of partial substitution of Sc3+ by Ti4+ in Sr2ScFeAsO3, Ca2ScFeAsO3 and Sr3Sc2Fe2As2O5 on their electrical properties. High levels of doping result in an increased carrier concentration and lead to the appearance of superconductivity with the onset of Tc up to 45 K.

Antiferromagnetism and metallic conductivity in Nb12O29

Abstract: AT the heart of the controversy about the microscopic origin of superconductivity in high-transition-temperature copper oxide superconductors is the question of whether or not the antiferromagnetism associated with the single-hole Cu2+ 3d9 state is of fundamental importance. To test whether this unconventional spin-mediated superconductivity might be electron/hole symmetric, oxides of the elements with single d-orbital electrons, such as Ti3+ (3d1), Nb4+ (4d1) and W5+ (5d1), are of particular interest. Localized magnetic spin states and magnetic ordering have never been observed previously in transition-metal oxides with one or two electrons in the 4d or 5d states, because of the preference for conventional d-band metallic conductivity or for metal–metal bonding. In exploring the possibility of a dl–d9 and ferroelec-tricity-superconductivity relationship in oxides (see, for instance, ref. 1), we have found that Nb12O29, a material with a 'crystallographic shear' structure, displays simultaneously both metallic conductivity, a signature of delocalized electrons, and local-moment magnetism with an antiferromagnetic ordering temperature of 12 K. This suggests that the bonding to oxygen of the 4d levels of early-transition-metal elements may not be sufficiently covalent to yield the kind of exotic conductivity (and thus exotic superconductivity) observed for copper oxides.

High-temperature superconductivity in layered nitrides β -Li x M NCl ( M = Ti, Zr, Hf): Insights from density functional theory for superconductors

Abstract: We present an ab initio analysis with density functional theory for superconductors (SCDFT) to understand the superconducting mechanism of doped layered nitrides \beta-Li$_x$MNCl (M=Ti, Zr, and Hf). The current version of SCDFT is based on the Migdal-Eliashberg theory and has been shown to reproduce accurately experimental superconducting-transition temperatures Tc of a wide range of phonon-mediated superconductors. In the present case, however, our calculated Tc$\leq$4.3 K (M=Zr) and $\leq$10.5 K (M=Hf) are found to be less than a half of the experimental Tc. In addition, Tc obtained in the present calculation increases with the doping concentration x, opposite to that observed in the experiment. Our results indicate that we need to consider some elements missing in the present SCDFT based on the Migdal-Eliashberg theory.

Preliminary study of a superconducting bulk magnet for the Maglev train

Abstract: One of the prospective applications of high critical temperature superconductors is a superconducting magnet for the magnetically levitated (Maglev) train. Development shows that RE (rare earth) BaCuO and LRE (light rare-earth) BaCuO superconductors prepared by melt processes have a high critical current density at 77 K and high magnetic fields. LRE-Ba-Cu-O bulk superconductors melt-processed in a reduced oxygen atmosphere, named oxygen-controlled-melt-growth (OCMG) process, are very promising for high field application as a superconducting permanent magnet with liquid nitrogen refrigeration. Compared to good quality melt-grown REBaCuO bulks, LREBaCuO bulks exhibit larger critical current densities in high magnetic fields and much improved irreversibility field at 77 K, implying that more effective flux pinning can be realized in a commercially feasible way. In this study, we discuss the possibility of a superconducting bulk magnet for a Maglev train. A preliminary design of the bulk magnet and also melt processing for REBaCuO and LREBaCuO bulk superconductors and their characteristic superconducting properties are presented.