Overhauser effect in individual InP/GaInP dots

Sizable nuclear spin polarization is pumped in individual InP/GaInP dots in a wide range of external magnetic fields B_ext=0-5T by circularly polarized optical excitation. We observe nuclear polarization of up to ~40% at Bext=1.5T and corresponding to an Overhauser field of ~1.2T. We find a strong feedback of the nuclear spin on the spin pumping efficiency. This feedback, produced by the Overhauser field, leads to nuclear spin bi-stability at low magnetic fields of Bext=0.5-1.5T. We find that the exciton Zeeman energy increases markedly, when the Overhauser field cancels the external field. This counter-intuitive result is shown to arise from the opposite contribution of the electron and hole Zeeman splittings to the total exciton Zeeman energy

Overhauser effect in individual InP/GaInP dots

Sizable nuclear spin polarization is pumped in individual InP/GaInP dots in a wide range of external magnetic fields B_ext=0-5T by circularly polarized optical excitation. We observe nuclear polarization of up to ~40% at Bext=1.5T and corresponding to an Overhauser field of ~1.2T. We find a strong feedback of the nuclear spin on the spin pumping efficiency. This feedback, produced by the Overhauser field, leads to nuclear spin bi-stability at low magnetic fields of Bext=0.5-1.5T. We find that the exciton Zeeman energy increases markedly, when the Overhauser field cancels the external field. This counter-intuitive result is shown to arise from the opposite contribution of the electron and hole Zeeman splittings to the total exciton Zeeman energy

Preparation and characterization of Bi26–2xMn2xMo10O69-d and Bi26.4Mn0.6Mo10–2yMe2yO69-d(Me = V, Fe) solid solutions

Received: 06.06.2017; accepted: 23.06.2017; published: 14.07.2017.Single phase samples of bismuth molybdate, Bi26Mo10O69, doped with Mn on the bismuth sublattice and V, Fe on the molybdenum sublattice were found to crystallize in the triclinic Bi26Mo10O69 structure at low doping levels and in the monoclinic Bi26Mo10O69 structure - at higher dopant concentration. The assumption that all Mn ions have an oxidation state of +2 was confirmed by means of magnetic measurement results analysis using Curie-Weiss law. Conductivity was investigated using impedance spectroscopy. The conductivity of Bi26.4Mn0.6Mo9.6Fe0.4O69-d was 1.2*10-2 S*cm-1 at 973 K and 2.2*10-4 S*cm-1 at 623 K, and the conductivity of Bi26.4Mn0.6Mo9.2V0.8O69-d was 2.2*10-3 S*cm-1 at 973 K and 2.2*10-5 S*cm-1 at 623 K

Suppression of nuclear spin diffusion at a GaAs/AlGaAs interface measured with a single quantum dot nano-probe

Nuclear spin polarization dynamics are measured in optically pumped individual GaAs/AlGaAs interface quantum dots by detecting the time-dependence of the Overhauser shift in photoluminescence (PL) spectra. Long nuclear polarization decay times of ~ 1 minute have been found indicating inefficient nuclear spin diffusion from the GaAs dot into the surrounding AlGaAs matrix in externally applied magnetic field. A spin diffusion coefficient two orders lower than that previously found in bulk GaAs is deduced.Comment: 5 pages, 3 figures, submitted to Phys Rev

Nonlinear graphene metamaterial

We demonstrate that the broadband nonlinear optical response of graphene can be resonantly enhanced by more than an order of magnitude through hybridization with a plasmonic metamaterial,while retaining an ultrafast nonlinear response time of ~1 ps. Transmission modulation close to ~1% is seen at a pump uence of ~0.03 mJ/cm^2 at the wavelength of ~1600 nm. This approach allows to engineer and enhance graphene's nonlinearity within a broad wavelength range enabling applications in optical switching, mode-locking and pulse shaping.Comment: The following article has been submitted to Applied Physics Letters. After it is published, it will be found at http://apl.aip.org

Interaction between the Arctic and Non-Arctic States in Scientific Research and Practical Development of the Geopolitical Potential of the Arctic

Aim. Reveal the methodological role of ideas about the geopolitical potential of the state in making managerial decisions in the development of the space of the Russian Arctic. The article presents an overview of fundamental research and articles by foreign authors that addresses the problem of realizing the geopolitical potential of the Arctic.Tasks. Development of the principles of geopolitical forecasting based on mathematical modeling of the geopolitical potential of the state and systematization of developments on the spatial development of the Russian Arctic as part of Greater Eurasia.Methods. Mathematical modeling of geopolitical processes, medium-term forecasting of the spatial development of the Russian Arctic in the face of challenges from foreign states claiming its natural resources and territorial waters.Results. It confirms the need to include scientific developments in the methodological apparatus of geopolitical research to identify qualitative and quantitative definitions of the geopolitical potential of the state, which contributes to ensuring the national security of Russia and improving its spatial development.Conclusions. The transition to the sixth technological mode is not limited to a radical transformation of the country’s production complex, but also implies the need to create a unified infrastructure architecture for the Greater Eurasia (“smart” Eurasia), into which the Russian Arctic organically fits

Synthesis, Structure, and Investigation of Bismuth Niobate Doped by Alkaline-Earth Elements

Polycrystalline samples with general formula Bi3

Russia’s Arctic Strategy in the Greater Eurasian Partnership

This study focuses on the role of the Arctic Strategy of Russia in the Great Eurasian Partnership.Aim. The study aims to identify the features of the Arctic Strategy of Russia in the Great Eurasian Partnership.Tasks. The development of principles of geopolitical forecasting and work with big data, with the aim of synchronizing the integration processes contradictory in nature and interests of the actors in Greater Eurasia, identifying the features of the geopolitical regionalization of Eurasia, and analyzing the global security analytics of the Great Eurasian Partnership in the coming “digital era”.Methods. The transition from the “analog” to the “digital era” at the beginning of the 21st century meant an essentially revolution in the data itself, which was associated with the emergence of their new quality — predictive. The methodology for research and forecasting the prospects of Eurasian integration is modeling the multi-agent interaction of geopolitical factors of coalitions based on mathematical game theory. The strategy of transition to a polycentric world order implies the need to move from “geopolitical fiction” to geopolitics, based on mathematical modeling of global geopolitics processes using game theory methods.Results. The geopolitical regionalization of Eurasia is a challenge to time. On the expanses of the Eurasian continent, several multi-format long-term “Eurasian projects” are increasingly clearly emerging. This is, firstly, the Eurasian Economic Union, secondly, the Chinese One Belt-One Way and, thirdly, Indo-Pacifica. The Russian Arctic is a region of the Great Eurasian Partnership. The tasks of the modern Arctic policy of Russia are focused on ensuring the priority growth of raw materials exports and industrial development of the Arctic territories, rather than on solving the problems of improving the quality of life of the local population, although in the Russian Arctic strategy until 2035 these tasks are formulated quite correctly.Conclusion. The analytics of the Eurasian partnership and the wording of expert assessments should be formed on the basis not only of political discourse, but also of exact sciences. In modern conditions, the development of scenario projects for the construction of the Great Eurasian Partnership, which includes the Greater Arctic (which, in turn, require an independent theoretical and methodological study), involves the full use of the apparatus of mathematical geopolitics (game theory), scenario modeling and big data technologies

Synthesis and crystal structure of a new hexagonal perovskite 7H-Ba7Li1.75Mn3.5O15.75 with Mn4+/Mn5+ charge distribution.

Our work describes the synthesis and crystal structure of a new hexagonal perovskite 7H-Ba7Li1.75Mn3.5O15.75with Mn4+/Mn5+charge distribution.</p