Local Electric Property Modification of Ferroelectric Tunnel Junctions Induced by Variation of Polarization Charge Screening Conditions under Measurement with Scanning Probe Techniques

Scanning tunneling spectroscopy in ultrahigh vacuum conditions and conductive atomic-force microscopy in ambient conditions were used to study local electroresistive properties of ferroelectric tunnel junctions SrTiO3/La0.7Sr0.3MnO3/BaTiO3. Interestingly, experimental current-voltage characteristics appear to strongly depend on the measurement technique applied. It was found that screening conditions of the polarization charges at the interface with a top electrode differ for two scanning probe techniques. As a result, asymmetry of the tunnel barrier height for the opposite ferroelectric polarization orientations may be influenced by the method applied to study the local tunnel electroresistance. Our observations are well described by the theory of electroresistance in ferroelectric tunnel junctions. Based on this, we reveal the main factors that influence the polarization-driven local resistive properties of the device under study. Additionally, we propose an approach to enhance asymmetry of ferroelectric tunnel junctions during measurement. While keeping the high locality of scanning probe techniques, it helps to increase the difference in the value of tunnel electroresistance for the opposite polarization orientations

Environmental Contaminants of Asiatic Deserts Ecosystems in relation to Plants Distribution and Structure

The focus of this research is on the salt/metalliferous pollutants because of their extreme toxicity, carcinogenicity, wide distribution and slow biodegradation under the harsh arid/semiarid environments. The extent of pollution of surface water and plants by various contents of salts, traces of heavy metals is presented for different regions of Zerafshan River Basin and Kyzylkum Desert. Soils and water contaminated with cadmium, copper, lead, zinc, selenium, arsenic, molybdenum, manganese, chromium, various oxidizers (Mn, NO3-, Fe +3, Al +3, ClO3-), NH4 and organic pollutants show natural colonization by species that have strategies of avoidance or tolerance to salt/metal toxities. Mapping of plant colonists of salts/metal contaminated soils, seed reproduction and cellular structures of tolerant taxa named as metallohalophytes are examined in the light of present knowledge of such strategies. Electrolytic adsorption and in situ immobilization technologies for cleaning pollutants of mining contaminated soils and underground water are suggested. Phytoremediation technology in the present case may offer a cost-effective and ecologically sound alternative.ion/salt contents, ICP-MS, glandular structures, metallohalophytes, phytoremediation, contaminated ecosystem, Kyzylkum Desert.

Розробка композиції на основі поліетилену і мікрочастинок мармуру, розкладуваної під дією ультрафіолетового випромінювання

Among the issues related to the disposal of polymers' waste is the design of cheap biodegradable polymeric materials, which are destroyed as a result of natural microbiological and chemical processes. Since the synthesis of biodegradable polymers is characterized by high material and energy costs, the filled biodegradable polymeric materials are more promising.This paper substantiates the feasibility of using marble microparticles as a filler for the biodegradable polymeric material based on high-pressure polyethylene whose decomposition rate increases under the conditions of ultraviolet radiation.Samples of the biodegradable polymeric material with the different content of a filler, the microparticles of marble (from 0 to 5.1 % by weight), were made; their physical-mechanical properties were investigated. It has been experimentally proven that UV radiation destroys polyethylene macromolecules into separate fragments with the formation of >C=O bonds, making it possible to decompose appropriate waste under the influence of sunlight.The feasibility of using the composition "high-pressure polyethylene – microparticles of marble" with a marble content of 1.78 % by weight has been confirmed for the manufacture of the sleeve and flat polymeric films for packaging and agricultural purposes, in particular, packing stretch film.Recommendations have been given on using the proposed biodegradable polymeric material. In particular, it is proposed that the production of articles from the "high-pressure polyethylene – microparticles of marble" composition should utilize a pre-obtained granulate of the required formulation. When making articles from the composition obtained directly in the extruder that molds the products, it is possible to apply adhesive additives to improve the interaction between a polymeric matrix and the filler's particlesОдним из направлений утилизации полимерных отходов является создание дешёвых биоразлагаемых (биодеградируемых) полимерных материалов, которые разрушаются в результате природных микробиологических и химических процессов. Поскольку синтез биоразлагаемых полимеров характеризуется высокими материало- и энергоёмкостью, то более перспективными являются наполненные биоразлагаемые полимерные материалы.Обоснована целесообразность применения микрочастиц мрамора в качестве наполнителя биоразлагаемого полимерного материала на основе полиэтилена высокого давления, скорость разложения которого увеличивается в условиях ультрафиолетового излучения.Получены образцы биоразлагаемого полимерного материала с различным содержанием наполнителя – микрочастиц мрамора (от 0 до 5,1 мас. %) и исследованы их физико-механические свойства. Экспериментально доказано, что УФ-облучение разрушает макромолекулы полиэтилена на отдельные фрагменты с образованием >С=О связей, что делает возможным разложение соответствующих отходов под воздействием солнечных лучей.Доказана целесообразность применения композиции «полиэтилен высокого давления – микрочастицы мрамора» с содержанием мрамора 1,78 масс. % для изготовления рукавных и плоских полимерных пленок упаковочного и сельскохозяйственного назначения, в частности упаковочной стрейтч-пленки.Разработаны рекомендации по применению предложенного биоразлагаемого полимерного материала. В частности изготовление продукции из композиции «полиэтилен высокого давления – микрочастицы мрамора» предложено осуществлять из предварительно полученного гранулята необходимого состава. В случае же изготовления продукции из композиции, получаемой непосредственно в экструдере, который формует продукцию, для улучшения взаимодействия полимерной матрицы с частицами наполнителя возможно использование адгезионных добавокОдним з напрямків утилізації полімерних відходів є створення дешевих біорозкладуваних (біодеградованих) полімерних матеріалів, які руйнуються в результаті природних мікробіологічних і хімічних процесів. Оскільки синтез біорозкладуваних полімерів характеризується високими матеріало- і енергоємністю, то більш перспективними є наповнені біорозкладувані полімерні матеріали.Обґрунтовано доцільність застосування мікрочастинок мармуру як наповнювача біорозкладуваного полімерного матеріалу на основі поліетилену високого тиску, швидкість розкладання якого збільшується в умовах ультрафіолетового випромінювання.Одержано зразки біорозкладуваного полімерного матеріалу з різним вмістом наповнювача – мікрочастинок мармуру (від 0 до 5,1 мас. %) та досліджено їхні фізико-механічні властивості. Експериментально доведено, що УФ-опромінення руйнує макромолекули поліетилену на окремі фрагменти з утворенням >С=О зв’язків, що робить можливим розкладання відповідних відходів під дією сонячного проміння.Доведено доцільність застосування композиції «поліетилен високого тиску – мікрочастинки мармуру» із вмістом мармуру 1,78 мас. % для виготовлення рукавних і плоских полімерних плівок пакувального та сільськогосподарського призначення, зокрема пакувальної стретч-плівки.Розроблено рекомендації щодо застосування запропонованого біорозкладуваного полімерного матеріалу. Зокрема виготовлення продукції з композиції «поліетилен високого тиску – мікрочастинки мармуру» запропоновано здійснювати з попередньо одержаного грануляту потрібного складу. У разі ж виготовлення продукції з композиції, одержуваної безпосередньо в екструдері, що формує продукцію, для покращення взаємодії полімерної матриці з частинками наповнювача можливе використання адгезійних добаво

Coulomb Correlations and Magnetic Anisotropy in ordered L10L1_0 CoPt and FePt alloys

We present results of the magneto-crystalline anisotropy energy (MAE) calculations for chemically ordered $L1_0$ CoPt and FePt alloys taking into account the effects of strong electronic correlations and spin-orbit coupling. The local spin density + Hubbard U approximation (LSDA+U) is shown to provide a consistent picture of the magnetic ground state properties when intra-atomic Coulomb correlations are included for both 3$d$ and 5$d$ elements. Our results demonstrate significant and complex contribution of correlation effects to large MAE of these material.Comment: revised version; 4 pages, 2 figure

Specific features of the electronic, spin, and atomic structures of a topological insulator Bi2Te2.4Se0.6

The specific features of the electronic and spin structures of a triple topological insulator Bi2Te2.4Se0.6, which is characterized by high-efficiency thermoelectric properties, have been studied with the use of angular- and spin-resolved photoelectron spectroscopy and compared with theoretical calculations in the framework of the density functional theory. It has been shown that the Fermi level for Bi2Te2.4Se0.6 falls outside the band gap and traverses the topological surface state (the Dirac cone). Theoretical calculations of the electronic structure of the surface have demonstrated that the character of distribution of Se atoms on the Te–Se sublattice practically does not influence the dispersion of the surface topological electronic state. The spin structure of this state is characterized by helical spin polarization. Analysis of the Bi2Te2.4Se0.6 surface by scanning tunnel microscopy has revealed atomic smoothness of the surface of a sample cleaved in an ultrahigh vacuum, with a lattice constant of ~4.23 Å. Stability of the Dirac cone of the Bi2Te2.4Se0.6 compound to deposition of a Pt monolayer on the surface is shown.This study was supported by the Ministry of Education and Science of the Russian Federation, the St. Petersburg State University (project nos. 11.38.271.2014 and 15.61.202.2015), and the Russian Foundation for Basic Research (project nos. 12-02-00226, 13-02-91327, 14-08-31110, and 13-02-12110). The research was also performed at the Resource Center “Physical Methods of Surface Investigation” at St. Petersburg State University. We are also grateful to collaborators of the Helmholtz-Zentrum (Berlin) for financial and technical support.Peer reviewe

Site- and spin-dependent coupling at the highly ordered h-BN/Co(0001) interface

Using photoelectron diffraction and spectroscopy, we explore the structural and electronic properties of the hexagonal boron nitride (h-BN) monolayer epitaxially grown on the Co(0001) surface. Perfect matching of the lattice parameters allows formation of a well-defined interface where the B atoms occupy the hollow sites while the N atoms are located above the Co atoms. The corrugation of the h-BN monolayer and its distance from the substrate were determined by means of R-factor analysis. The obtained results are in perfect agreement with the density functional theory (DFT) predictions. The electronic structure of the interface is characterized by a significant mixing of the h-BN and Co states. Such hybridized states appear in the h-BN band gap. This allows to obtain atomically resolved scanning tunneling microscopy (STM) images from the formally insulating 2D material being in contact with ferromagnetic metal. The STM images reveal mainly the nitrogen sublattice due to a dominating contribution of nitrogen orbitals to the electronic states at the Fermi level. We believe that the high quality, well-defined structure and interesting electronic properties make the h-BN/Co(0001) interface suitable for spintronic applications.L.V.Ya. acknowledges the RSF (Grant No. 16-42-01093). A.V.T., V.O.S., K.A.B., O.Yu.V., and D.Yu.U. acknowledge St. Petersburg State University for research Grant No. 11.65.42.2017. M.V.K. and I.I.O. acknowledge the RFBR (Grant No. 16-29-06410). C.L. acknowledges the DFG (Grant Nos. LA655-17/1 and LA655-19/1).Peer reviewe

The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe

The preponderance of matter over antimatter in the early Universe, the dynamics of the supernova bursts that produced the heavy elements necessary for life and whether protons eventually decay --- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our Universe, its current state and its eventual fate. The Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed plan for a world-class experiment dedicated to addressing these questions. LBNE is conceived around three central components: (1) a new, high-intensity neutrino source generated from a megawatt-class proton accelerator at Fermi National Accelerator Laboratory, (2) a near neutrino detector just downstream of the source, and (3) a massive liquid argon time-projection chamber deployed as a far detector deep underground at the Sanford Underground Research Facility. This facility, located at the site of the former Homestake Mine in Lead, South Dakota, is approximately 1,300 km from the neutrino source at Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino charge-parity symmetry violation and mass ordering effects. This ambitious yet cost-effective design incorporates scalability and flexibility and can accommodate a variety of upgrades and contributions. With its exceptional combination of experimental configuration, technical capabilities, and potential for transformative discoveries, LBNE promises to be a vital facility for the field of particle physics worldwide, providing physicists from around the globe with opportunities to collaborate in a twenty to thirty year program of exciting science. In this document we provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess.Comment: Major update of previous version. This is the reference document for LBNE science program and current status. Chapters 1, 3, and 9 provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess. 288 pages, 116 figure

Two-particle correlations in azimuthal angle and pseudorapidity in inelastic p + p interactions at the CERN Super Proton Synchrotron

Results on two-particle ΔηΔϕ correlations in inelastic p + p interactions at 20, 31, 40, 80, and 158 GeV/c are presented. The measurements were performed using the large acceptance NA61/SHINE hadron spectrometer at the CERN Super Proton Synchrotron. The data show structures which can be attributed mainly to effects of resonance decays, momentum conservation, and quantum statistics. The results are compared with the Epos and UrQMD models.ISSN:1434-6044ISSN:1434-605