Non-Dirac topological surface states in (SnTe)n≥2_{n\geq2}(Bi2_2Te3_3)m=1_{m=1}

A new type of topological spin-helical surface states was discovered in layered van der Waals bonded (SnTe)$_{n=2,3}$(Bi$_2$Te$_3$)$_{m=1}$ compounds which comprise two covalently bonded band inverted subsystems, SnTe and Bi$_2$Te$_3$, within a building block. This novel topological states demonstrate non-Dirac dispersion within the band gap. The dispersion of the surface state has two linear sections of different slope with shoulder feature between them. Such a dispersion of the topological surface state enables effective switch of the velocity of topological carriers by means of applying an external electric field

First principles quasiparticle damping rates in bulk lead

First principles calculations of the damping rates (inverse inelastic lifetimes) of low energy quasiparticles in bulk Pb are presented. Damping rates are obtained both for excited electrons and holes with energies up to 8 eV on a set of k vectors throughout the Brillouin zone (BZ). Strong localization effects in the calculated lifetimes are found. Averaged over the BZ inelastic lifetimes versus quasiparticle energy are reported as well. In addition, the effect of the spin-orbit induced splitting in the band structure on the calculated lifetimes in Pb is investigated.Comment: 10 pages, 8 figures, 5 table

E.K. Zavoiskii and NMR: Analysis of laboratory notebooks and rerun of experiments

© 2015 AIP Publishing LLC. An analysis of the laboratory notebooks of E. K. Zavoiskii, the discoverer of electron paramagnetic resonance, shows that in 1941 he began trying to observe NMR of various nuclei in condensed matter. A rerun of his NMR experiments shows that the sensitivity of the "grid current" method that he developed was adequate for reliable detection of NMR of protons in water solutions of paramagnetic salts. The reason for the poor reproducibility of Zavoiskii's NMR experiments was insufficient the homogeneity of the magnetic field of the electromagnets he used

Mechanisms of regulation of invasive processes in phytoplankton on the example of the north-eastern part of the Black Sea

© 2016, Springer Science+Business Media Dordrecht. In the north-eastern part of the Black Sea, the seasonal complexes of dominant species of phytoplankton were fixed: small-celled diatom (spring), coccolithophores (late spring, early summer) and large diatoms (summer and autumn). In May–June 2005 and 2006, two invasive species of marine diatoms Chaetoceros throndsenii (maximal abundance 1.92 × 105 cells/l) and Chaetoceros minimus (1.6 × 105 cells/l) were recorded. These species have been incorporated in the complex of the late spring and early summer and grew simultaneously with the coccolithophore Emiliania huxleyi. The coccolithophore was dominant species, whose abundance had reached the level of a bloom. C. throndsenii was observed over the entire area from the coast to the centre of the sea; C. minimus were recorded at coastal stations and only at two stations of the open sea. Stratification of the water mass and the low (below the Redfield) ratio of nitrogen to phosphorus were observed at this time. Then, C. throndsenii was not marked even once, and C. minimus has been registered once on a shelf in June 2011. Experimental studies (2005) have shown that intensive growth C. throndsenii requires the simultaneous addition of nitrogen and phosphorus in a ratio close to the Redfield ratio. C. minimus shows the intensive growth only at high concentrations of phosphorus and at low nitrogen-to-phosphorus ratio (the experiment was carried out in June 2011). Mathematical modelling shows that C. throndsenii and Emiliania huxleyi form a stable couple whose growth is limited by different factors: the diatoms by nitrogen and the coccolithophores by phosphorus. C. minimus might not be able to form a stable couple with coccolithophores because they have the same limiting factor, i.e. phosphorus. However, this species could become the dominant one, if low (0.5–1) nitrogen-to-phosphorus ratio conditions were stable for more than 2 months. However, this scenario is improbable in natural circumstances since the existence of this complex seasonal rarely exceeds 1.5 months

VIOLATION OF INFORMATION ECOLOGY IN MEDIA SPACE

The extreme “pollution” of the global information space has a negative impact on the social well-being of the population for media space is a kind of social space covered by the media. It is necessary to create an effective system of legal protection and social guarantees so that any citizen can receive minimal social protection and be protected from the negative impact of the adverse ecology of the mass media. Not everyone who is experiencing intense exposure to the media is aware of its negative effects including “fatigue syndrome”. To prevent it, D. Lewis proposes the following algorithm: use all information technologies of business and everyday communication; improve the methods of studying and processing data; set the right priorities for their analysis and use [26]. All media and actors that interact with them must master information culture, for which it is necessary to train specialists in the field of media ecology who are aware of the influence of media and social technologies on people’s feelings, thoughts, values and behavior. So far, experts on media ecology do not have a sufficient theoretical basis for conducting sociological research and identifying how the media forces the audience to structure what it sees, hears and feels in a certain way. Today’s media (especially electronic) can have a violent and undesirable effect - this is not only a psychological but also a philosophical, social and cultural problem that affects both children and adults. “Information anarchy” leads not only to moderate negative consequences but in some cases to “information ecocide” - destruction of traditional information and the media. Countering the contamination of the information environment should include the following steps: development of requirements for the content creation; monitoring of the collection, storage, processing and destruction of information; development of criteria for assessing the use of information. It is necessary to introduce a single rating system for information products, which will allow users to evaluate the quality of information sources according to the following criteria: purity of information; work on creating content; source coverage; quality (completeness) of information; sources of specific data sets; social-demographic characteristics of potential users

Electronic and spin structure of a family of Sn-based ternary topological insulators

We report the bulk and surface electronic properties and spin polarization of a rich family of Sn-based ternary topological insulators studied by means of first-principles calculations within the framework of density functional theory. These compounds exist with the following stoichiometries: SnX2Te4,SnX4Te7, and SnBi6Te10 (X = Sb and Bi). Where a septuple layer or a quintuple layer and septuple layer blocks alternate along the hexagonal axis. We reveal that the bulk band gap in these compounds is about 100 meV and recognize a strong dependence of the spin polarization on the cleavage surface. The calculated spin polarization reaches 85% in some cases, that is one of the highest predicted values hitherto. Since the electron spin polarization is a relevant parameter for spintronics technology, this new family is suitable for applications within this field

Surface states and their possible role in the superconductivity of MgB2

We report layer-Korringa-Kohn-Rostocker calculations for bulk and surface states as well as the corresponding angle resolved photoemission (ARPES) intensities of MgB2. Our theoretical results reproduce very well the recent ARPES data by Uchiyama et al., cond-mat/0111152. At least two surface states are assigned. Consequences of SFS on the anisotropy of the upper critical fields and other properties in the superconducting state of small grains in micropowder samples are briefly discussed.Comment: 4pages, 6figures, corrected typos, references adde

EPR Study of the Vanadium Ions in Mg2SiO4 Crystal

Vanadium-doped forsterite crystal has been studied with X-band electron paramagnetic resonance (EPR) spectroscopy. The sample was grown by the Czochralski technique in an argon atmosphere with 2 vol% of hydrogen. The EPR spectrum of the sample at T = 15 K is predominantly represented by the V4+ ion signals that possess a characteristic eight-line hyperfine structure and are observed close to g = 2. The observation of the two magnetically nonequivalent centers in the angular dependence in the (ab) crystal plane and one center in the (ac) and (bc) planes, combined with the published optical spectroscopy data, unambiguously show that the V4+ ions are located at the silicon lattice site. Principal values of the hyperfine A and g-tensor and magnetic axes orientations of the V4+ centers have been determined. The orientation disorder of the V4+ centers has been found around the crystalline c axis but not in the (ab) crystal plane. The angular variation of the hyperfine component linewidth is described best with a disorder range of ±3. 0°. © 2012 Springer-Verlag Wien