Anisotropic Electron Spin Lifetime in (In,Ga)As/GaAs (110) Quantum Wells

Anisotropic electron spin lifetimes in strained undoped (In,Ga)As/GaAs (110) quantum wells of different width and height are investigated by time-resolved Faraday rotation and time-resolved transmission and are compared to the (001)-orientation. From the suppression of spin precession, the ratio of in-plane to out-of-plane spin lifetimes is calculated. Whereas the ratio increases with In concentration in agreement with theory, a surprisingly high anisotropy of 480 is observed for the broadest quantum well, when expressed in terms of spin relaxation times.Comment: 4 pages, 4 figures, revise

Quantum phase transition in the dioptase magnetic lattice

The study of quantum phase transitions, which are zero-temperature phase transitions between distinct states of matter, is of current interest in research since it allows for a description of low-temperature properties based on universal relations. Here we show that the crystal green dioptase Cu_6Si_6O_18 . 6H_2O, known to the ancient Roman as the gem of Venus, has a magnetic crystal structure, formed by the Cu(II) ions, which allows for a quantum phase transition between an antiferromagnetically ordered state and a quantum spin liquid.Comment: 6 pages, 5 figures, EPL, in pres

Electron-phonon and spin-phonon coupling in NaV2_{2}O5_{5}: charge fluctuations effect

We show that the asymmetric crystal environment of the V site in the ladder compound NaV$_{2}$O$_{5}$ leads to a strong coupling of vanadium 3d electrons to phonons. This coupling causes fluctuations of the charge on the V ions, and favors a transition to a charge-ordered state at low temperatures. In the low temperature phase the charge fluctuations modulate the spin-spin superexchange interaction, resulting in a strong spin-phonon coupling.Comment: Europhysics Letters, to be publishe

Site-specific force-distance characteristics on NaCl(001): Measurements versus atomistic simulations

A scanning force microscope was used to measure the frequency shift above various atomic sites on a NaCl(001) surface at 7K. The data was converted to force and compared to the results of atomistic simulations using model NaCl and MgO tips. We find that the NaCl tip demonstrates better agreement in the magnitude of the forces in experiments, supporting the observation that the tip first came into contact with the sample. Using the MgO tip as a model of the originally oxidized silicon tip, we further demonstrate a possible mechanism for tip contamination at low temperatures.Peer reviewe

Анализ современных технологий систем поддержания пластового давления при разработке нефтяных месторождений

Анализ геологических особенностей строения пластов, состава добываемых флюидов, типов вод, применяемых в системах поддержания пластового давления. Анализ современных методов поддержания пластового давления.Analysis of the geological features of the structure of reservoirs, the composition of the produced fluids, the types of water used in the systems for maintaining reservoir pressure. Analysis of modern methods of maintaining reservoir pressure

Magnetic and electronic properties of M-Ba-Cu-O (M: Y, Er, Eu)

Various high-Tc superconductors of the La-(Ba,Sr)-Cu-O and the M-Ba-Cu-O systems with M = Y, Er, and Eu have been prepared by the solid-state reaction method. Single-phase samples with no additional diffraction peaks as verified by x-ray diffraction (XRD) measurements have been obtained. Measurements of the electrical resistivity and of the magnetization showed sharp superconducting transitions with a width of 1 K. The measurements of the magnetic susceptibility have been extended above room temperature up to 770 K. There is clear evidence for the formation of a magnetic moment in all M-Ba-Cu-O samples. Monochromated x-ray photoelectron spectroscopy (MXPS) valence band and x-ray photoelectron spectroscopy (XPS) core level spectra have been measured on various samples at room temperature and at liquid nitrogen temperatur

Анализ использования золошлакового материала Красноярской ТЭЦ-2 для получения товарного продукта

Объектом исследования в работе являются технологии утилизации золы с получением товарного продукта. Целью выпускной квалификационной работы является выполнение аналитического обзора литературных данных по использованию золошлаковых отходов, складируемых на золоотвале №2 Красноярской ТЭЦ -2, с целью производства товарного продукта. В процессе исследования проводился аналитический обзор по литературным источникам с целью выяснения достижений мировой науки техники в рассматриваемой области. В результате исследования разработана технологическая схема переработки золы и шлака в продукт для дальнейшего использования в отрасли производства строительных материалов.The object of research in the work are the technologies for the utilization of ash to obtain a marketable product. The aim of the final qualification work is to perform an analytical review of the literature on the use of ash and slag waste stored at ash dump No. 2 of the Krasnoyarsk power plant 2, with the aim of producing a marketable product. In the course of the study, an analytical review of literary sources was carried out in order to ascertain the achievements of the world science of technology in the field under consideration. As a result of the study, a technological scheme was developed for processing ash and slag into a product for further use in the building materials industry

Evidence for local lattice distortions in giant magnetocapacitive CdCr2S4

Raman scattering experiments on CdCr2S4 single crystals show pronounced anomalies in intensity and frequency of optical phonon modes with an onset temperature T*=130 K that coincides with the regime of giant magnetocapacitive effects. A loss of inversion symmetry and Cr off-centering are deduced from the observation of longitudinal optical and formerly infrared active modes for T<T_c=84 K. The intensity anomalies are attributed to the enhanced electronic polarizability of displacements that modulate the Cr-S distance and respective hybridization. Photo doping leads to an annihilation of the symmetry reduction. Our scenario of multiferroic effects is based on the near degeneracy of polar and nonpolar modes and the additional low energy scale due to hybridization.Comment: 4 pages, 6 figure