Mass-renormalized electronic excitations at (π\pi, 0) in the superconducting state of Bi2Sr2CaCu2O8+δBi_{2}Sr_{2}CaCu_{2}O_{8+\delta}

Using high-resolution angle-resolved photoemission spectroscopy on $Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta}$, we have made the first observation of a mass renormalization or "kink" in the E vs. $\vec k$ dispersion relation localized near $(\pi, 0)$. Compared to the kink observed along the nodal direction, this new effect is clearly stronger, appears at a lower energy near 40 meV, and is only present in the superconducting state. The kink energy scale defines a cutoff below which well-defined quasiparticle excitations occur. This effect is likely due to coupling to a bosonic excitation, with the most plausible candidate being the magnetic resonance mode observed in inelastic neutron scattering

Zn₁₋ₓMgₓSe single crystals as a functional material for optoelectronics

Structure, mechanical, optical, and electro-physical properties of single crystals of Zn₁₋ₓMgₓSe (0.03 0.12) have been found to be suitable as a functional material for manufacturing of thermally stable polarizing, electro-optical, and multifunctional devices intended to be operated under intense irradiation in near and medium IR range.Проведенi комплекснi дослiдження структурних, механiчних, оптичних та електрофiзичних властивостей монокристалiв твердого розчину Zn₁₋ₓMgₓSe (0,03 0,12) придатнi в якостi функцiонального материалу для виготовлення на їх основi термостабiльних поляризацiйних, електрооптичних та багатофункцiональних елементiв, призначених для роботи з iнтенсивним випромiнюванням ближнього та середнього IЧ дiапазонiв.Исследованы структурные, механические, оптические и электрофизические свойства монокристаллов твердых растворов Zn₁₋ₓMgₓSe (0,03 0,12) пригодны в качестве функционального материала для изготовления на их основе термостабильных поляризационных, электрооптических и многофункциональных элементов, предназначенных для работы с интенсивным излучением ближнего и среднего ИК диапазонов

Influence of Ca and Mg doping on the microstructure and optical properties of YAG ceramics

Ceramics of yttrium aluminum garnet doped with Ca or Mg are produced by solid state reaction under vacuum sintering. The influence of CaO and MgO additives themselves on microstructure and optical properties of YAG ceramics is investigated. Ceramics of Mg-doped YAG is transparent while ceramics of Ca-doped YAG is fully opaque due to high concentration of residual porosity into later. Changing concentration of Ca affects significantly on the grain growth, the average grain size increase with increasing of Ca concentration. Changing concentration of Mg from 0.05 to 0.5 at.% doesn't influence on grain size of the ceramics. It is proposed that liquid appears on the grain boundaries of the ceramics due to CaO additive. This liquid causes increasing the diffusion of components through the grain boundaries that speed up the grain growth and traps the pores while no such liquid exists for MgO additive. This difference is determined by the different ways of interaction of CaO and MgO with the basic YAG components Al₂O₃ and Y₂O₃. It is determined that the Mg concentration ranges in vicinity of 0.15 at.% Mg to produce Mg:YAG ceramics of higher transparency

Structure of thermally evaporated bismuth selenide thin films

The Bi₂Se₃ thin films with thicknesses d = 7-420 nm were grown by thermal evaporation in vacuum of stoichiometric n-Bi₂Se₃ crystals onto heated glass substrates under optimal technological conditions determined by the authors. The growth mechanism, microstructure, and crystal structure of the prepared thin films were studied using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. It was established that the prepared thin films were polycrystalline, with composition close to the stoichiometric one, did not contain any phases apart from Bi₂Se₃, were of a high structural quality, and the preferential growth direction [001] corresponded to the direction of a trigonal axis C₃ in a hexagonal lattice. The films, like the initial crystal, exhibited n-type conductivity. It was shown that with increasing film thickness, the grain size and the film roughness remain practically the same at thicknesses d << 100 nm, and after that increase, reaching their saturation values at d ~ 300 nm. It follows from the results obtained in this work that using the method of thermal evaporation in vacuum from a single source, one can prepare thin n-Bi₂Se₃ films of a sufficiently high structural quality with a composition close to the stoichiometric one and the preferential growth orientation