The mechanism of high temperature superconductivity is not resolved for so long because the normal state of cuprates is not yet understood. Here we show that the normal state pseudo-gap exhibits an unexpected non-monotonic temperature dependence, which rules out the possibility to describe it by a single mechanism such as superconducting phase fluctuations. Moreover, this behaviour, being remarkably similar to the behaviour of the charge ordering gap in the transitionmetal dichalcogenides, completes the correspondence between these two classes of compounds: the cuprates in the PG state and the dichalcogenides in the incommensurate charge ordering state reveal virtually identical spectra of one-particle excitations as function of energy, momentum and temperature. These results suggest that the normal state pseudo-gap, which was considered to be very peculiar to cuprates, seems to be a general complex phenomenon for 2D metals. This may not only help to clarify the normal state electronic structure of 2D metals but also provide new insight into electronic properties of 2D solids where the metal-insulator and metal-superconductor transitions are considered on similar basis as instabilities of particle-hole and particle-particle interaction, respectively.PACS numbers: 74.25. Jb, 74.72.Hs, 71.15.Mb In the normal state, the conventional superconductors are metals and the superconductivity emerges as a particle-particle instability, known as Cooper pairing, resulting in a superconducting gap (SG) in the spectrum of one-particle excitations. The superconducting cuprates were found to be different, exhibiting a pseudo-gap (PG) already in the normal state [1], and, since its discovery, the PG towers as an impregnable wall on the way to understanding the high-T c superconductivity [2], either foreshadowing the SG [3] or interfering with it [4]. In spite of recent progress [5,6,7,8,9] in disentangling the SG and PG phenomena, the origin of the PG remains unclear. It is still widely believed that the PG is peculiar to the cuprates [2,10] and that it closes above T * [10, 11] but a characteristic behaviour which can help to uniquely identify its origin among many possibilities is missing [2,9]. Here we show that the PG in cuprates exhibits an unexpected non-monotonic temperature dependence, which rules out the possibility to describe it by a single mechanism such as superconducting phase fluctuations. Moreover, this behaviour, being remarkably similar to the behaviour of the charge ordering gap in the transition-metal dichalcogenides [12], completes the correspondence between these two classes of compounds: the cuprates in the PG state and the dichalcogenides in the incommensurate charge ordering state reveal virtually identical spectra of one-particle excitations as function of energy, momentum and temperature. This allows one not only to conclude that the governing contribution to the PG in cuprates comes from an incommensurate charge ordering but also to consider the PG as a general phenomenon for 2D metals.Although one ...

The Tm-Ba-Cu-O solder can be successfully used to produce a superconductive joint between MT-YBCO parts. The peculiarities of solidification, phase formation, structure transformations and electromagnetic properties of MT-YBCO soldered with Tm Ba 2 Cu 3 O 7-/ are discussed.

We propose an empirical approach to estimate the quality of superconducting joints (welds) between blocks of bulk high temperature superconductors (HTS). As a measuring value, we introduce a quality factor of the joint and show its natural correlation with the joint's critical current density. Being simple and non-destructive, this approach is considered to be quite important to solve the problem of the utilization of HTS in large scale applications. The approach has been applied to characterize the joint's quality of melt-processed Y-123 joined by Tm-123 solder.

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Методом функцiонала густини в узагальненому ґрадiєнтному наближенні за допомогою пакета програм ABINIT проведено моделювання електронних та пружних властивостей систем, що складають композит TiC-TiB 2 . Виконано аналіз електронних спектрів дибориду титану, карбіду титану та побудованої надкомірки композиту TiC-TiB 2 . Встановлено, що основною особливістю електронної структури досліджених систем є розташування рівня Фермі у локальному мінімумі енергетичної залежності густини електронних станів, що формується переважно 3d-електронними станами атомів Титану. Показано, що незначна дифузія атомів Карбону та Бору в композиті TiC-TiB 2 не призводить до кардинальних змін електронної структури композиту. Розрахований модуль всебічного стиснення надкомірки композиту TiC-TiB 2 практично не відрізняється від такого для TiB 2 .