Direct Evidence of Two Superconducting Gaps in FeSe0.5_{0.5}Te0.5_{0.5}: SnS-Andreev Spectroscopy and Lower Critical Field

We present direct measurements of the superconducting order parameter in nearly optimal FeSe$_{0.5}$Te$_{0.5}$ single crystals with critical temperature $T_C \approx 14$ K. Using intrinsic multiple Andreev reflection effect (IMARE) spectroscopy and measurements of lower critical field, we directly determined two superconducting gaps, $\Delta_L \approx 3.3 - 3.4$ meV and $\Delta_S \approx 1$ meV, and their temperature dependences. We show that a two-band model fits well the experimental data. The estimated electron-boson coupling constants indicate a strong intraband and a moderate interband interaction

In-plane optical response of Bi2Sr2CuO6

We report on infrared reflectivity measurements of the $ab$-plane response of superconducting Bi$_2$Sr$_2$CuO$_6$ single crystals. The frequency dependent conductivity has a maximum near 700 cm$^{-1}$ at room temperature, which shifts to lower frequency and merges with a Drude-peak below 100 K. We attribute the unusual behaviour of the mid-infrared conductivity to low frequency transitions between electronic bands of mainly BiO character near the $\overline{M}$ point. The linear temperature dependence of the low-frequency resistivity can be followed down to approximately 40 K where it saturates.Comment: Revtex, 4 pages, 4 postscript figures, Phys. Rev. B, in pres

Direct evidence of two superconducting gaps in FeSe<inf>0.5</inf>Te<inf>0.5</inf>: SnS-Andreev spectroscopy and the lower critical field

© 2016, Pleiades Publishing, Inc.We present direct measurements of the superconducting order parameter in nearly optimal FeSe Te single crystals with the critical temperature TC ≈ 14 K. Using the intrinsic multiple Andreev reflection effect (IMARE) spectroscopy and measurements of the lower critical field, we directly determined two superconducting gaps, ΔL ≈ 3.3−3.4 meV and ΔS ≈ 1 meV, and their temperature dependences. We show that a twoband model fits well the experimental data. The estimated electron–boson coupling constants indicate a strong intraband and a moderate interband interaction

Systematics of c-axis Phonons in the Thallium and Bismuth Based Cuprate Superconductors

We present grazing incidence reflectivity measurements in the far infrared region at temperatures above and below Tc for a series of thallium (Tl2Ba2CuO6, Tl2Ba2CaCu2O8) and bismuth (Bi2Sr2CuO6, Bi2Sr2CaCu2O8, and Bi(2-x)Pb(x)Sr2CaCu2O8) based cuprate superconductors. From the spectra, which are dominated by the c-axis phonons, longitudinal frequencies (LO) are directly obtained. The reflectivity curves are well fitted by a series of Lorentz oscillators. In this way the transverse (TO) phonon frequencies were accurately determined. On the basis of the comparative study of the Bi and Tl based cuprates with different number of CuO2 layers per unit cell, we suggest modifications of the assignment of the main oxygen modes. We compare the LO frequencies in Bi2Sr2CaCu2O8 and Tl2Ba2Ca2Cu3O10 obtained from intrinsic Josephson junction characteristics with our measurements, and explain the discrepancy in LO frequencies obtained by the two different methods.Comment: 8 pages Revtex, 6 eps figures, 3 tables, to appear in Phys. Rev.

Production of {\pi}+ and K+ mesons in argon-nucleus interactions at 3.2 AGeV

First physics results of the BM@N experiment at the Nuclotron/NICA complex are presented on {\pi}+ and K+ meson production in interactions of an argon beam with fixed targets of C, Al, Cu, Sn and Pb at 3.2 AGeV. Transverse momentum distributions, rapidity spectra and multiplicities of {\pi}+ and K+ mesons are measured. The results are compared with predictions of theoretical models and with other measurements at lower energies.Comment: 29 pages, 20 figure

ОСОБЛИВОСТІ МЕХАНІКИ ПОДРІБНЕННЯ ГРУНТОВОГО ШАРУ ПРИ ОБРОБЦІ ЙОГО ЗУБЧАСТИМ РОБОЧИМ ОРГАНОМ

 Chernozems ofUkraineare one of the main values of the state and its strategic resource. The quality and fertility of soils largely depends on the processing method and on the design features of the processing tool. In order to intensify the process, improve the quality, reduce energy costs in the treatment of soils, the design of a gear working organ (GWO) is proposed. The task is to test the work capacity of the new GWO, to investigate the mechanics of loosening the soil when processing it with a working organ and to develop a model for the interaction of the soil with the surfaces of the teeth of the working organ.  Чорноземи України є однією з найбільших коштовностей держави та її стратегічним ресурсом. Якість та родючість ґрунтів значною мірою залежать від способу обробки та від конструктивних особливостей оброблювального інструменту. З метою інтенсифікації процесу, підвищення якості, зниження енергозатрат при обробці ґрунту запропоновано конструкцію зубчастого робочого органу (ЗРО). Поставлено задачу випробовувати працездатність нового ЗРО, дослідити механіку подрібнення ґрунту при обробці його зубчастим робочим органом та розробити моделі взаємодії ґрунту з поверхнями зубців робочого органу.

ВПЛИВ АСИМЕТРІЇ ЦИКЛУ НА ВЕЛИЧИНУ ЕФЕКТИВНОГО КОЕФІЦІЄНТА КОНЦЕНТРАЦІЇ НАПРУЖЕНЬ

Samples of low-alloyed steel with stress concentration are investigated in asymmetrical cycles conditions. Mechanism of forming of residual stresses is described. Limit amplitude diagrams are presented.Проведені дослідження на опір втомі зразків з концентратором із сталі 09Г2С. Розглянуто механізм формування в зоні концентратора залишкових напружень в умовах асиметрії циклу. Представлені діаграми граничних амплітуд

Analysis of electronic properties frommagnetotransport measurements on Ba(Fe1-xNix)2As2 thin films

We performed a detailed structural, magnetotransport, and superconducting analysis of thin epitaxial Ba(Fe1-xNix)2As2 films with Ni doping of x = 0.05 and 0.08, as prepared by pulsed laser deposition. X-ray diffraction studies demonstrate the high crystalline perfection of the films, which have a similar quality to single crystals. Furthermore, magnetotransport measurements of the films were performed in magnetic fields up to 9 T. The results we used to estimate the density of electronic states at the Fermi level, the coefficient of electronic heat capacity, and other electronic parameters for this compound, in their dependence on the dopant concentration within the framework of the Ginzburg-Landau-Abrikosov-Gorkov theory. The comparison of the determined parameters with measurement data on comparable Ba(Fe1-xNix)2As2 single crystals shows good agreement, which confirms the high quality of the obtained films