[en] On the basis of an analysis of theoretical and numerical studies of model systems and of experiments on superconductivity in doped C₆₀, polyacenes, and the cuprate high-temperature superconductors, we propose that a purely electronic mechanism of superconductivity requires structures at an intermediate scale or mesoscale. Specifically, we address the crucial question of how high-temperature superconducting pairing on the mesoscale can arise from purely repulsive electronic interactions

No abstract available

[en] Short communication

No abstract available

[en] Five sessions were held at the Sanibel Symposium 2008. 14 speakers, 5 chair persons for these 5 sessions and a number of posters are presented at the poster sessions.

[en] An investigation has been carried out of strength properties of single crystals of LuBa₂Cu₃O_7-x having submicrometre (74-245 nm) cross-sectional dimensions and oriented in the (100) direction. It has been established that the tensile strength of these crystals is independent of the cross-sectional dimensions, being equal to 4.3±0.7 GPa at 78 K. The maximum measured value of tensile strength has been found to be equal to 4.8 GPa. (author)

[en] In this work, we report on the effect of Y3+ doping on structural, mechanical and electrical properties of Bi-2202 phase. Samples of Bi2Sr1.9Ca0.1−xYxCu2O7+δ with x=0, 0.025, 0.05, 0.075 and 0.10 are elaborated in air by conventional solid state reaction and characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) combined with EDS spectroscopy, density, Vickers microhardness and resistivity measurements. A good correlation between the variations of the bulk density and the Vickers microhardness with doping is obtained. The SEM photograph shows that the samples are composed of grains with a flat shape that characterizes the Bi-based cuprates. Quantitative EDS analysis confirms the reduction of Ca content and the increase of Y content when x is increased. The variation of resistivity with temperature shows that only samples with x=0, 0.025 and 0.05 present an onset transition to the superconducting state. The higher onset transition temperature is obtained for x=0.025 and is about 93.62K. The transition is wide and is realized in two steps confirming then the presence of the low Tc Bi-2201 phase in the samples. For x=0.075 and 0.10, a transition to a semiconducting state is seen at low temperatures. Some physical parameters are extracted from these curves and discussed. (Author)

[en] The stability of charge ordered phases is doping dependent, with different materials having particularly stable ordered phases. In the half filled charge ordered phases of the cuprates this occurs at one eighth doping, whereas in charge-stripe ordered La_2−xSr_xNiO_4+δ there is enhanced stability at one third doping. In this paper we discuss the known details of the charge-stripe order in La_2−x Sr_xNiO_4+δ, and how these properties lead to the one third doping stability.

[en] Parameters of hamiltonian of crystalline field of compouns satisfactorily decribing both neutron spectra and experimental data on magnetic susceptibility of monocrystal are determined on the ground of data on Nd₂CuO₄ polycrytalline specimen

[en] The idea of existence of a Fermi surface with ImΣ(k_F,μ) ≠0 has been described in cuprate superconductors by comparing it with the Anderson-Luttinger liquid theory and with the marginal Fermi liquid theory. The Fermi surface is formed by paired (but unbound) coherencons. Evolution of these entities in cuprates superconductors is clarified. Effect of the paired coherencon Fermi surface on the normal state and superconducting state properties of cuprate superconductors is discussed. (author). 22 refs., 9 figs., 1 tab