Large magnetic gap at the Dirac point in Bi2Te3/MnBi2Te4 heterostructures.

Magnetically doped topological insulators enable the quantum anomalous Hall effect (QAHE), which provides quantized edge states for lossless charge-transport applications1-8. The edge states are hosted by a magnetic energy gap at the Dirac point2, but hitherto all attempts to observe this gap directly have been unsuccessful. Observing the gap is considered to be essential to overcoming the limitations of the QAHE, which so far occurs only at temperatures that are one to two orders of magnitude below the ferromagnetic Curie temperature, TC (ref. 8). Here we use low-temperature photoelectron spectroscopy to unambiguously reveal the magnetic gap of Mn-doped Bi2Te3, which displays ferromagnetic out-of-plane spin texture and opens up only below TC. Surprisingly, our analysis reveals large gap sizes at 1 kelvin of up to 90 millielectronvolts, which is five times larger than theoretically predicted9. Using multiscale analysis we show that this enhancement is due to a remarkable structure modification induced by Mn doping: instead of a disordered impurity system, a self-organized alternating sequence of MnBi2Te4 septuple and Bi2Te3 quintuple layers is formed. This enhances the wavefunction overlap and size of the magnetic gap10. Mn-doped Bi2Se3 (ref. 11) and Mn-doped Sb2Te3 form similar heterostructures, but for Bi2Se3 only a nonmagnetic gap is formed and the magnetization is in the surface plane. This is explained by the smaller spin-orbit interaction by comparison with Mn-doped Bi2Te3. Our findings provide insights that will be crucial in pushing lossless transport in topological insulators towards room-temperature applications.

Negative Longitudinal Magnetoresistance from the Anomalous N=0 Landau Level in Topological Materials.

Negative longitudinal magnetoresistance (NLMR) is shown to occur in topological materials in the extreme quantum limit, when a magnetic field is applied parallel to the excitation current. We perform pulsed and dc field measurements on Pb_{1-x}Sn_{x}Se epilayers where the topological state can be chemically tuned. The NLMR is observed in the topological state, but is suppressed and becomes positive when the system becomes trivial. In a topological material, the lowest N=0 conduction Landau level disperses down in energy as a function of increasing magnetic field, while the N=0 valence Landau level disperses upwards. This anomalous behavior is shown to be responsible for the observed NLMR. Our work provides an explanation of the outstanding question of NLMR in topological insulators and establishes this effect as a possible hallmark of bulk conduction in topological matter.

Entanglement and manipulation of the magnetic and spin-orbit order in multiferroic Rashba semiconductors.

Entanglement of the spin-orbit and magnetic order in multiferroic materials bears a strong potential for engineering novel electronic and spintronic devices. Here, we explore the electron and spin structure of ferroelectric α-GeTe thin films doped with ferromagnetic Mn impurities to achieve its multiferroic functionality. We use bulk-sensitive soft-X-ray angle-resolved photoemission spectroscopy (SX-ARPES) to follow hybridization of the GeTe valence band with the Mn dopants. We observe a gradual opening of the Zeeman gap in the bulk Rashba bands around the Dirac point with increase of the Mn concentration, indicative of the ferromagnetic order, at persistent Rashba splitting. Furthermore, subtle details regarding the spin-orbit and magnetic order entanglement are deduced from spin-resolved ARPES measurements. We identify antiparallel orientation of the ferroelectric and ferromagnetic polarization, and altering of the Rashba-type spin helicity by magnetic switching. Our experimental results are supported by first-principles calculations of the electron and spin structure.

Multiple-stable anisotropic magnetoresistance memory in antiferromagnetic MnTe.

Commercial magnetic memories rely on the bistability of ordered spins in ferromagnetic materials. Recently, experimental bistable memories have been realized using fully compensated antiferromagnetic metals. Here we demonstrate a multiple-stable memory device in epitaxial MnTe, an antiferromagnetic counterpart of common II-VI semiconductors. Favourable micromagnetic characteristics of MnTe allow us to demonstrate a smoothly varying zero-field antiferromagnetic anisotropic magnetoresistance (AMR) with a harmonic angular dependence on the writing magnetic field angle, analogous to ferromagnets. The continuously varying AMR provides means for the electrical read-out of multiple-stable antiferromagnetic memory states, which we set by heat-assisted magneto-recording and by changing the writing field direction. The multiple stability in our memory is ascribed to different distributions of domains with the Néel vector aligned along one of the three magnetic easy axes. The robustness against strong magnetic field perturbations combined with the multiple stability of the magnetic memory states are unique properties of antiferromagnets.

Massive and massless Dirac fermions in Pb1-xSnxTe topological crystalline insulator probed by magneto-optical absorption.

Dirac fermions in condensed matter physics hold great promise for novel fundamental physics, quantum devices and data storage applications. IV-VI semiconductors, in the inverted regime, have been recently shown to exhibit massless topological surface Dirac fermions protected by crystalline symmetry, as well as massive bulk Dirac fermions. Under a strong magnetic field (B), both surface and bulk states are quantized into Landau levels that disperse as B(1/2), and are thus difficult to distinguish. In this work, magneto-optical absorption is used to probe the Landau levels of high mobility Bi-doped Pb0.54Sn0.46Te topological crystalline insulator (111)-oriented films. The high mobility achieved in these thin film structures allows us to probe and distinguish the Landau levels of both surface and bulk Dirac fermions and extract valuable quantitative information about their physical properties. This work paves the way for future magnetooptical and electronic transport experiments aimed at manipulating the band topology of such materials.

Vertical external cavity surface emitting PbTe/CdTe quantum dot lasers for the mid-infrared spectral region.

Optically pumped vertical external cavity surface emitting lasers (VECSELS) emitting in the mid-infrared range are demonstrated with an active structure based on PbTe quantum dots (QDs) embedded in CdTe. In contrast to Stranski-Krastanov QDs, the PbTe QDs are fabricated by a strain-free synthesis method consisting of a molecular beam epitaxy growth step followed by a post-growth-annealing step. The laser emission of the VECSELs covers a wavelength range between 3.5 and 4.3 µm by changing the temperature from 85 to 240 K. The threshold power is lower than 100 mW(P) and the output power is more than 50 mW(P) at low temperature.

[Clinical justification of medico-psychological care to the victims of technogenic accidents and catastrophes with prevalence of anxious and depressive symptoms of non-psychotic register].

In the article the clinical justification of medico-psychological care to the victims of technogenic accidents and catastrophes with prevalence of anxious and depressive symptoms of non-psychotic register is described. The necessity of differentiated approach is analyzed in accomplishing of psychotherapy of this contingent of patients taking into account the high level of anxiety, emotional stress, decreased mood, low levels of the quality of life in the remote period of strong stressful factor's action.

[Protective platelet features in fibrocavernous tuberculosis]. / Zashchitnye osobennosti trombotsitov pri fibrozno-kavernoznom tuberkuleze.

Light and electron microscopy was used to study platelets in acute and chronic pulmonary tuberculosis. The structure of platelets was demonstrated to be altered depending on the pattern of a tuberculous process. The ratio of alpha-granules, dense glanules, mitochondria, and lysosomes was also changed. The role of platelets in an immunological process was studied. The redistribution of glanules in the platelets finds its new reflection in the light of the psycho- and neutropic actions of the granules contained.

[Unusually high number of B-chromosomes and mosaicism among them in the Asiatic forest mouse Apodemus peninsulae (Rodentia, Muridae)]. / Neobychno vysokoe chislo B-khromosom i mozaitsizm po nim u Aziatskoi lesnoi myshi Apodemus peninsulae (Rodentia, Muridae).

Karyological analysis of Apodemus peninsulae from Western Siberia was made. It was established that animals under study are characterized both by interindividual variation of B-chromosome number or polymorphism which was described previously and by intraindividual variation or mosaicism. Diploid numbers are 55-57, 58-61, 61-65 and 68-72, i. e. studied animals possess 3, 4, 5 and 5 cell clones, respectively. The highest number of B-chromosomes in mammals was found to be 24.

[Nature and role of accessory chromosomes in silver-gray foxes. IV. The behavior of accessory chromosomes in meiosis]. / Issledovanie prirody i roli dobavochnykh khromosom serebristochernykh lisits. Soobschchenie IV. Povedenie dobavochnykh khromosom v meioze.

Comparison of chromosome number at somatic and spermatogonial mitoses has demonstrated the increase in the number of additional chromosomes in cells of germinal tissue. This may evidence a mechanism of B-chromosomes accumulation in foxes. B-chromosomes may lag as univalents, may form bivalent associations, or occasionally form trivalents at the stage of diakinesis-metaphase I, and they may associate with macrobivalents (A-chromosome bivalents). The analysis of metaphase II has shown that the distribution of B-chromosomes in the second metaphase is random resulting in gametes with various numbers of B-chromosomes.

[Experience with treating complicated forms of abscessing pneumonia in children]. / Opyt lecheniia oslozhnennykh form abstsediruiushchikh pnevmonii u detei

Under observation were 157 patients with different forms of abscessing pneumonias. Pleural complicaitons were noted in 113 patients (about 60%). The complex treatment was employed in all patients (intensive antibacterial therapy, immunotherapy, bacteriophage, administration of protein preparations, vitamin-therapy, fresh blood transfusion, artery system and by means of percutaneous catheterization of th subclavian vein. The results of the treatment are described.