[en] The authors address vortex state and dynamics of mixed wave superconductors in the framework of Ginzburg-Landau theory. They find that the s- and d-wave components of a single vortex in the d+is-state exhibit two-fold symmetry and the intrinsic Hall effect displays a different angle dependence from that of d-wave state. For d_x²-y2 + id_xy-wave superconductors, a Ginzburg-Landau theory is developed from a microscopic theory with a strong coupling term being included. In the absence of a magnetic field, the theory predicts a pure d_x²-y² state at T > T* and a second order phase transition at T^- to a time-reversal-symmetry-breaking d_x²_-y² + id_xy state, with T* being very small. In a magnetic field, the strong coupling effect could lead to that a d_x²-_y² + id_xy state is always established, albeit with decreasing d_xy amplitude with increasing temperature

[en] We develop a theory to understand various types of electronic collective behaviors in manganites, such as magnetic, charge, and orbital orderings. Starting from an electronic model with strong correlations, we derive an effective Hamiltonian by utilizing the projection perturbation techniques, in which the orbital degeneracy of e_g electrons in Mn ions are taken into account. Interplay of spin, charge and orbital degree of freedom leads to different magnetic and electronic structures in manganites

[en] Using a simple model of the moving vortex lattice, the washboard effect in the mixed state of high-T_c superconductors, which is due to the interference between the intrinsic oscillation of the vortex lattice and the applied ac driving current, is investigated by numerical simulation. The obtained numerical results are in good agreement with recent experimental measurements on YBCO crystal [Phys. Rev. Lett. 74, 3684 (1995)]. We also study the case when the ac driving current consists of two frequencies, and observe that the corresponding washboard effect is related not only to the two basic frequencies of the ac current but also to their combination terms. (orig.)

[en] Using the Wang-Ting model and including the influence of the thermal fluctuation on the flux motions, we have performed numerical simulation of the scaling behaviour in the negative Hall resistivity region of the high-T_c superconductors for the first time. A scaling law with an exponent β∼1.7 at low magnetic fields has been found in our simulation for the YBCO system, which is in good agreement with the experimental observation. (author)

[en] We have solved the Bogoliubov--de Gennes equation for a clean, one-dimensional mesoscopic superconducting ring threaded by a magnetic flux Φ. We show that the superfluid velocity is driven directly by Φ while the relative motion of the pair of electrons is independent of Φ. Meanwhile, the fluxoid quantization is obtained straightforwardly. More importantly, we have also calculated the supercurrent numerically and self-consistently and find it is periodic in Φ with the period Φ_s≡hc/2e for Φ_s≤Φ_d=(mv dL/ℎπ)Φ_s and with the period Φ₀≡hc/e for Φ_d<Φ_s, which arises from mesoscopic effects

[en] Based upon the well-known normal-core model for flux lines in high-κ superconductors and by correctly taking into account the backflow current due to pinning forces, we analytically derived the longitudinal resistivity ρ_xx and the Hall resistivity ρ_xy as functions of magnetic field in the region of flux flow. The present results qualitatively explain all the essential features of recent experiments on ρ_xy. In particular, we demonstrate that the observed negative Hall resistivity at low magnetic field in certain high-T_c superconductors can be explained in terms of the existence of pinning forces in the sample

[en] The nonlinear a.c. response of the flux motion in type II superconductors is studied using a single flux motion model. We have performed a numerical simulation and evaluated the a.c. response against frequency. Three cases of applied current are considered: a single-frequency a.c. current, an a.c. current of two frequencies and a d.c. plus an a.c. current. We find that, when the Lorentz driving force is greater than the pinning force, there exists a crossover frequency below which a strong nonlinear a.c. response is exhibited. We also find that the value of this crossover frequency has a linear relation with the ratio of the Lorentz and the pinning forces. (author)

[en] Using a tight-binding model Hamiltonian and applying the Jordan-Wigner transformation, we have investigated the Aharonov-Casher (AC) effect for many neutral hard-core bosons in one-dimensional (1D) mesoscopic rings with the self-induced AC phase included. The total energy and the persistent fluxon current are analytically derived for 1D perfect lattices. More importantly, it is suggested that, in the absence of the external AC flux, the self-sustained AC flux state could be the ground state of a system with weak disorder. The possibility of experimenal observations is briefly discussed

[en] We have investigated the superconducting phase difference dependence of Andreev levels and Josephson current through a mesoscopic normal-metal layer in contact with two superconducting electrodes with s-wave and d-wave pairing symmetry (S_sNSd junction). It is shown that, regardless of the junction length, due to the sign change of the d-wave order parameter under suitable arrangements, the zero-energy point of Andreev levels for the negative process appears at var-phi=0. In particular, at zero temperature, the amplitude of the total Josephson current through the point contact S_sNSd junction could be enhanced by the sign change of the d-wave order parameter. However, for an S_sNSd junction of special length, the amplitude of Josephson current may be suppressed by this sign change. Moreover, as a special case, the midgap surface states discovered by Hu [Phys. Rev. Lett. 72, 1526 (1994)] are recovered naturally. copyright 1996 The American Physical Society

[en] The application of glass fiber reinforced plastics (GFRPs) as insulating materials for the superconducting (SC) magnet coils of the International Thermonuclear Experimental Reactor (ITER) fusion device imposes high demands on the material performance. Therefore, GFRPs with improved mechanical and electrical properties are of special interest. One of the most promising matrix materials for higher radiation resistance is the cyanate ester system. Two innovative insulation systems with boron-free S-glass fiber reinforcements and cyanate ester based matrix compositions were irradiated in the TRIGA reactor (Vienna, Austria) to neutron fluences of 1x10²¹, 1x10²² and 5x10²² m^-2 (E>0.1 MeV). After irradiation, swelling and weight loss were measured prior to static and dynamic tensile as well as interlaminar shear testing at 77 K