890 research outputs found
Extra Spin-Wave mode in Quantum Hall systems. Beyond the Skyrmion Limit
We report on the observation of a new spin mode in a quantum Hall system in
the vicinity of odd electron filling factors under experimental conditions
excluding the possibility of Skyrmion excitations. The new mode having
presumably zero energy at odd filling factors emerges at small deviations from
odd filling factors and couples to the spin-exciton. The existence of an extra
spin mode assumes a nontrivial magnetic order at partial fillings of Landau
levels surrounding quantum Hall ferromagnets other then the Skyrmion crystal.Comment: 9 pages, 4 figure
Quasiparticle Interference on the Surface of Topological Crystalline Insulator Pb(1-x)Sn(x)Se
Topological crystalline insulators represent a novel topological phase of
matter in which the surface states are protected by discrete point
group-symmetries of the underlying lattice. Rock-salt lead-tin-selenide alloy
is one possible realization of this phase which undergoes a topological phase
transition upon changing the lead content. We used scanning tunneling
microscopy (STM) and angle resolved photoemission spectroscopy (ARPES) to probe
the surface states on (001) PbSnSe in the topologically
non-trivial (x=0.23) and topologically trivial (x=0) phases. We observed
quasiparticle interference with STM on the surface of the topological
crystalline insulator and demonstrated that the measured interference can be
understood from ARPES studies and a simple band structure model. Furthermore,
our findings support the fact that PbSnSe and PbSe have
different topological nature.Comment: 5 pages, 4 figure
Proposal for realizing Majorana fermions in chains of magnetic atoms on a superconductor
We propose an easy-to-build easy-to-detect scheme for realizing Majorana fermions at the ends of a chain of magnetic atoms on the surface of a superconductor. Model calculations show that such chains can be easily tuned between trivial and topological ground states. In the latter, spatially resolved spectroscopy can be used to probe the Majorana fermion end states. Decoupled Majorana bound states can form even in short magnetic chains consisting of only tens of atoms. We propose scanning tunneling microscopy as the ideal technique to fabricate such systems and to probe their topological properties
CD1d-dependent immune suppression mediated by regulatory B cells through modulations of iNKT cells
Regulatory B cells (Breg) express high levels of CD1d that presents lipid antigens to invariant natural killer T (iNKT) cells. The function of CD1d in Breg biology and iNKT cell activity during inflammation remains unclear. Here we show, using chimeric mice, cell depletion and adoptive cell transfer, that CD1d–lipid presentation by Bregs induces iNKT cells to secrete interferon (IFN)-γ to contribute, partially, to the downregulation of T helper (Th)1 and Th17-adaptive immune responses and ameliorate experimental arthritis. Mice lacking CD1d-expressing B cells develop exacerbated disease compared to wild-type mice, and fail to respond to treatment with the prototypical iNKT cell agonist α-galactosylceramide. The absence of lipid presentation by B cells alters iNKT cell activation with disruption of metabolism regulation and cytokine responses. Thus, we identify a mechanism by which Bregs restrain excessive inflammation via lipid presentation
Electron energy relaxation under terahertz excitation in (Cd1−xZnx)3As2 Dirac semimetals
We demonstrate that measurements of the photo-electromagnetic effect using terahertz laser radiation provide an argument for the existence of highly conductive surface electron states with a spin texture in Dirac semimetals (Cd₁-xZnx)₃As
Current Trends in Global Supply Chain Management Investment Policy
Abstract- To achieve the Sustainable Development Goals of the world economy, significant financial resources and global supply chain are needed. Priority issues are related to the use of investment resources. Almost all sectors of the economy have a real need for investment. Domestic investments is not enough for countries to implement effective structural policies and upgrade fixed assets. They are forced to attract foreign investment. The annual requirements for international investment reach several trillion US dollars. However, foreign investors are in no hurry to expand investments in the economy of foreign countries. Moreover, in 2017-2019 there is a decrease in global direct foreign investment flows. This is largely due to a noticeable reduction in US investment in the economies of the European Union and China as a result of the tightening of the American protectionism policy pursued by the D. Trump administration and the US Federal Reserve to strengthen regulation of foreign companies in the US market. A decrease in the level of international investment under the worsening business climate in the world leads to the increased competition between countries for attracting foreign investment
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