Observation of extremely slow hole spin relaxation in self-assembled quantum dots

We report the measurement of extremely slow hole spin relaxation dynamics in small ensembles of self-assembled InGaAs quantum dots. Individual spin orientated holes are optically created in the lowest orbital state of each dot and read out after a defined storage time using spin memory devices. The resulting luminescence signal exhibits a pronounced polarization memory effect that vanishes for long storage times. The hole spin relaxation dynamics are measured as a function of external magnetic field and lattice temperature. We show that hole spin relaxation can occur over remarkably long timescales in strongly confined quantum dots (up to ~270 us), as predicted by recent theory. Our findings are supported by calculations that reproduce both the observed magnetic field and temperature dependencies. The results suggest that hole spin relaxation in strongly confined quantum dots is due to spin orbit mediated phonon scattering between Zeeman levels, in marked contrast to higher dimensional nanostructures where it is limited by valence band mixing.Comment: Published by Physical Review

Application of Pareto and Ishikawa Diagrams for Identification of Dangerous Production Factors

Приведены результаты анализа возможности применением для идентификации опасных и вредных производственных факторов диаграмм Парето и Исакавы. Показано, что применение диаграмм позволяет выявить значимые и приоритетные факторы, что позволяет целенаправленно направлять материальные ресурсы на улучшение условий труда и повышение безопасности на рабочих местах.The results of the analysis of the possibility of using Pareto and Isakawa diagrams to identify dangerous and harmful production factors are presented. It is shown that the use of diagrams allows us to identify significant and priority factors, which allows us to purposefully direct material resources to improve working conditions and improve safety in the workplace

TRANSPORT AND THE GREENHOUSE EFFECT

The article presents the results of the analysis of the impact of carbon dioxide emissions from diesel locomotive exhaust gases on the formation of the greenhouse effect. It is shown that the role of rail transport is very noticeable and carbon dioxide emissions into the environment should be taken into account in general greenhouse gas emissions.В статье приведены результаты анализ воздействия выброса углекислого газа с отработавшими газами тепловозов на образование парникового эффекта. Показано, что роль железнодорожного транспорта весьма заметна и выбросы углекислого газа в окружающую среду следует учитывать в общем выбросы парниковых газов

Waste of Reinforced Concrete Products in Railway Transport as a Material Resource

При эксплуатации железных дорог образуется много отходов - в официальном классификаторе их не менее шестисот. На сегодняшний день большой проблемой является утилизация железобетонных изделий с истекшим сроком эксплуатации. Принцип разумного расхода и оптимизации бюджета заключается в повторном использовании железобетонных изделий на железнодорожном транспорте, если они не утратили своих функциональных свойств. Это означает, что вместо утилизации часть изделий можно повторно использовать на железной дороге, в производстве или быту повторно.When operating railways, a lot of waste is generated - there are at least six hundreds of them in the official classifier. To date, a big problem is the disposal of reinforced concrete products with expired service life. The principle of reasonable expenditure and budget optimization is the reuse of reinforced concrete products in railway transport, if they have not lost their functional properties. This means that instead of recycling, some of the products can be reused on the railway, in production or in everyday life

Electrical control over single hole spins in nanowire quantum dots

Single electron spins in semiconductor quantum dots (QDs) are a versatile platform for quantum information processing, however controlling decoherence remains a considerable challenge. Recently, hole spins have emerged as a promising alternative. Holes in III-V semiconductors have unique properties, such as strong spin-orbit interaction and weak coupling to nuclear spins, and therefore have potential for enhanced spin control and longer coherence times. Weaker hyperfine interaction has already been reported in self-assembled quantum dots using quantum optics techniques. However, challenging fabrication has so far kept the promise of hole-spin-based electronic devices out of reach in conventional III-V heterostructures. Here, we report gate-tuneable hole quantum dots formed in InSb nanowires. Using these devices we demonstrate Pauli spin blockade and electrical control of single hole spins. The devices are fully tuneable between hole and electron QDs, enabling direct comparison between the hyperfine interaction strengths, g-factors and spin blockade anisotropies in the two regimes

Semiconductor Spintronics

Spintronics refers commonly to phenomena in which the spin of electrons in a solid state environment plays the determining role. In a more narrow sense spintronics is an emerging research field of electronics: spintronics devices are based on a spin control of electronics, or on an electrical and optical control of spin or magnetism. This review presents selected themes of semiconductor spintronics, introducing important concepts in spin transport, spin injection, Silsbee-Johnson spin-charge coupling, and spindependent tunneling, as well as spin relaxation and spin dynamics. The most fundamental spin-dependent nteraction in nonmagnetic semiconductors is spin-orbit coupling. Depending on the crystal symmetries of the material, as well as on the structural properties of semiconductor based heterostructures, the spin-orbit coupling takes on different functional forms, giving a nice playground of effective spin-orbit Hamiltonians. The effective Hamiltonians for the most relevant classes of materials and heterostructures are derived here from realistic electronic band structure descriptions. Most semiconductor device systems are still theoretical concepts, waiting for experimental demonstrations. A review of selected proposed, and a few demonstrated devices is presented, with detailed description of two important classes: magnetic resonant tunnel structures and bipolar magnetic diodes and transistors. In most cases the presentation is of tutorial style, introducing the essential theoretical formalism at an accessible level, with case-study-like illustrations of actual experimental results, as well as with brief reviews of relevant recent achievements in the field.Comment: tutorial review; 342 pages, 132 figure