—New preparation methods of superconducting materials and other multicomponent systems. We discuss the synthesis of multicomponent oxides such as the superconducting phase YBa2Cu307 in the form of powders and thick fílms. They are prepared from hydrolyzed solutions which yield viscous gels suitable for spin-coating or precipitates, precursors of ceramics. We discuss the role of the precursors, ...

We derive the expressions needed to interpret experiments relating to interplane magnetic coupling in YBa2Cu3O6+x and related materials, and use the results to interpret measurements of the optical magnon energy in YBa2Cu3O6.2 and of the NMR “cross-relaxation” rate in Y2Ba4Cu7O15. We estimate J⊥ ∼ 14 meV in both materials, and χmax/μB ∼ 100 states/eV-Cu in Y2Ba4Cu7O15 at T = 100K. We show that ...

We consider the competition between superconducting, charge ordered, and metallic phases in layered molecular crystals with the theta and beta(") structures. Applying slave-boson theory to the relevant extended Hubbard model, we show that the superconductivity is mediated by charge fluctuations and the Cooper pairs have d(xy) symmetry. This is in contrast to the kappa-(BEDT-TTF)(2)X family, for...

Transport properties of a superconductor-semiconductor-superconductor (Su-Sm-Su) junction with superlattice structure are investigated. Differential resistance as a function of voltage shows oscillatory behavior under the irradiation of radio-frequency (rf) waves with the specific frequency of 1.77 GHz regardless of the superconducting materials and the junction geometries. Experimental data ar...

We show that superconductors with broken time-reversal symmetry have very specific magnetic and electric responses to inhomogeneous heating. A local heating of such superconductors induces a magnetic field with a profile that is sensitive to the presence of domain walls and crystalline anisotropy of superconducting states. A nonstationary heating process produces an electric field and a charge ...

A quantum pseudo-spin model with random spin sizes is introduced to study the effects of charging-energy disorder on the superconducting transition in granular superconducting materials. Charging-energy effects result from the small electrical capacitance of the grains when the Coulomb charging energy is comparable to the Josephson coupling energy. In the pseudo-spin model, randomness in the sp...

Superconducting states with different internal topology are discussed for the layered high-T c materials. If the time inversion symmetry is broken, the superconductivity is determined not only by the symmetry of the superconducting state, but also by the topology of the ground state. The latter is determined the integer-valued momentum-space topological invariant N. The current carrying boundar...

We predict by first-principles calculations that p-doped graphane is an electron-phonon superconductor with a critical temperature above the boiling point of liquid nitrogen. The unique strength of the chemical bonds between carbon atoms and the large density of electronic states at the Fermi energy arising from the reduced dimensionality give rise to a giant Kohn anomaly in the optical phonon ...

The quasiparticle relaxation time in superconducting films has been measured as a function of temperature using the response of the complex conductivity to photon flux. For tantalum and aluminum, chosen for their difference in electron-phonon coupling strength, we find that at high temperatures the relaxation time increases with decreasing temperature, as expected for electron-phonon interactio...