Circular photon drag effect in bulk tellurium

The circular photon drag effect is observed in a bulk semiconductor. The photocurrent caused by a transfer of both translational and angular momenta of light to charge carriers is detected in tellurium in the mid-infrared frequency range. Dependencies of the photocurrent on the light polarization and on the incidence angle agree with the symmetry analysis of the circular photon drag effect. Microscopic models of the effect are developed for both intra- and inter-subband optical absorption in the valence band of tellurium. The shift contribution to the circular photon drag current is calculated. An observed decrease of the circular photon drag current with increase of the photon energy is explained by the theory for inter-subband optical transitions. Theoretical estimates of the circular photon drag current agree with the experimental data.Comment: 8 pages, 4 figure

Terahertz radiation due to random grating coupled surface plasmon polaritons

We report on terahertz (THz) radiation under electrical pumping from a degenerate semiconductor possessing an electron accumulation layer. In InN, the random grating formed by topographical defects provides high-efficiency coupling of surface plasmon polaritons supported by the accumulation layer to the THz emission. The principal emission band occupies the 2-6 THz spectral range. We establish a link between the shape of emission spectra and the structural factor of the random grating and show that the change of slope of power dependencies is characteristic for temperature-dependent plasmonic mechanisms. The super-linear rise of a THz emission intensity on applied electric power provides advantage of such materials in emission yield.Comment: 4 pages, 4 figure

Structural and Magnetic Properties of “Thick” Microwires Produced by the Ulitovsky-Taylor Method

The structural and magnetic physical properties of initial and annealed Co-rich microwires in a glass shell with the diameter D = 70-125 μm and the diameter of the amorphous metallic core d = 70-95 μm, produced by the Ulitovsky–Taylor method, have been studied. The magnetic characteristics, in particular, the saturation field HS and the coercive force HC of the samples were found to depend on annealing temperature. The obtained experimental data was explained by the structural peculiarities of the microwires. The near-surface values of HS and HC were found to be larger than the bulk values by a factor of 5–10. These experimental data have been explained by the existence of structural and chemical ingomogeneities in the near-surface layer, which are inherent in amorphous materials. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3531

Opto-Electronic Characterization of Three Dimensional Topological Insulators

We demonstrate that the terahertz/infrared radiation induced photogalvanic effect, which is sensitive to the surface symmetry and scattering details, can be applied to study the high frequency conductivity of the surface states in (Bi1-xSbx)2Te3 based three dimensional (3D) topological insulators (TI). In particular, measuring the polarization dependence of the photogalvanic current and scanning with a micrometre sized beam spot across the sample, provides access to (i) topographical inhomogeneity's in the electronic properties of the surface states and (ii) the local domain orientation. An important advantage of the proposed method is that it can be applied to study TIs at room temperature and even in materials with a high electron density of bulk carriers.Comment: 6 pages, 4 figure

A new species of Stanieria(Cyanobacteria) isolated from a small pool on Mexican Riviera

Among coccoid Cyanobacteria, special reproductive cells have been found: exocytesand baeocytes. These cells can be very different in terms of development. Exocytesare attached to the apical part of the mother cells. Baeocytesdevelop inside the mother cells, forming robust sheaths (Fig.1.A;B). In the phylogenetic sense, representatives of exocytesproduction belong to the CHROOCOCCALES, as opposed to baeocytesproducers which occur in the PLEUROCAPSALES (Fig.2.). In our research we found coccoid cyanobacteria, that produce baeocytesfrom the Mexican Riviera on the Yucatan Peninsul

Spin photocurrents and circular photon drag effect in (110)-grown quantum well structures

We report on the study of spin photocurrents in (110)-grown quantum well structures. Investigated effects comprise the circular photogalvanic effect and so far not observed circular photon drag effect. The experimental data can be described by an analytical expression derived from a phenomenological theory. A microscopic model of the circular photon drag effect is developed demonstrating that the generated current has spin dependent origin.Comment: 6 pages, 3 figure

CYANOMARGARITA GEN. NOV. (NOSTOCALES, CYANOBACTERIA): CONVERGENT EVOLUTION RESULTING IN A CRYPTIC GENUS

Two populations of Rivularia-like cyanobacteria were isolated from ecologically diverse and biogeographically distant sites. One population was from an unpolluted stream in the Kola Peninsula of Russia, whereas the other was from a wet wall in the Grand Staircase-Escalante National Monument, a desert park-land in Utah. Though both were virtually indistinguishable from Rivularia in field and cultured material, they were both phylogenetically distant from Rivularia and the Rivulariaceae based on both 16S rRNA and rbcLX phylogenies. The new putative cryptic genus Cyanomargarita, with proposed type species C. melechinii sp. nov., and additional putative species C. calcarea are described herein. A new family for these taxa, the Cyanomargaritaceae, is proposed for this new genus