Submicron-sized MoRe-doped Si-MoRe Josephson junctions with a low specific capacitance

Abstract We start with a short look at the problem of low-capacitance Josephson junctions, its history, and actual state-of-the-art. It is argued that such devices are important for applications requiring nonhysteretic current-voltage characteristics since reduction of capacitance by several times makes it possible to increase the device resistance by the same amount while keeping the McCumber-Stewart damping parameter unaltered. Moreover, at very high frequencies the capacitance in the RCSJ circuit with a parallel connection starts to shunt the superconducting current component due to reduction of the corresponding reactance inversely proportional to C. Hence, to extend the operating frequency range of a Josephson junction its capacitance should be as small as possible. As a solution of a new type of the Josephson device, less resistive and with smaller capacitance, we propose and realize a submicron-sized trilayer with tens nm-thick Si interlayer doped by metallic ultra-small inclusions and superconducting Mo-Re alloy electrodes

Pinning and trapped field in MgB2- and MT-YBaCuO bulk superconductors manufactured under pressure

The relevant pinning centers of Abrikosov vortices in MgB$_{2}$–based materials are oxygen-enriched Mg-B-O inclusions or nanolayers and inclusions of MgB$_{x}$ (x>4) phases. The high critical current densities, j$_{c}$, of 10$^{6}$ and 10$^{3}$A/cm$^{2}$ at 1 and 8.5 T, respectively, at 20 K can be achieved in polycrystalline materials (prepared at 2 GPa) containing a large amount of admixed oxygen. Besides, oxygen can be incorporated into the MgB$_{2}$ structure in small amounts (MgB$_{1.5}$O$_{0.5}$), which is supported by Auger studies and calculations of the DOS and the binding energy. The j$_{c}$ of melt textured YBa$_{2}$Cu$_{3}$O$_{7-δ }$ (or Y123)-based superconductors (MT-YBaCuO) depends not only on the perfectness of texture and the amount of oxygen in the Y123 structure, but also on the density of twins and micro-cracks formed during the oxygenation (due to shrinking of the c-lattice parameter). The density of twins and microcracks increases with the reduction of the distance between Y$_{2}$BaCuO$_{5}$ (Y211) inclusions in Y123. At 77 K j$_{c}$=8⋅10$^{4}$ A/cm$^{2}$ in self-field and j$_{c}$=10$^{3}$ A/cm$^{2}$ at 10 Т were found in materials oxygenated at 16 MPa for 3 days with a density of twins of 22–35 per μm (thickness of the lamellae: 45-30 nm) and a density of micro-cracks of 200–280 per mm. Pinning can occur at the points of intersection between the Y123 twin planes and the Y211 inclusions. MTYBaCuO at 77 K can trap 1.4 T (38×38×17 mm, oxygenated at 0.1 MPa for 20 days) and 0.8 T (16 mm in diameter and 10 mm thick with 0.45 mm holes oxygenated at 10 MPa for 53 h). The sensitivity of MgB$_{2}$ to magnetic field variations (flux jumps) complicates estimates of the trapped field. At 20 K 1.8 T was found for a block of 30 mm in diameter and a thickness of 7.5 mm and 1.5 T (if the magnetic field was increased at a rate of 0.1 T) for a ring with dimensions 24×18 mm and a thickness of 8 mm

Об оптимизации смешанной зарядной инфраструктуры электробусов для городских маршрутов

Objectives. When transition from a fleet of diesel buses to a fleet of electric buses, it is important to optimize the charging infrastructure, which combines the slow-charging technologies at the depot overnight and fast recharging at the terminals of the routes. The purpose of the study is to create models and methods for developing the cost-effective solutions for selecting this type of charging infrastructure for a fleet of electric buses serving the city route system, taking into account a number of specific conditions. The operation of the fleet and charging infrastructure is modeled both for the depot at night and for the terminal stops in the most representative period of the day, characterized by the highest intensity of passenger traffic and maximum power consumption.Methods. Methods of set theory, graph theory and linear approximation are used.Results. A mathematical model has been developed for the problem of optimizing a mixed-type charging infrastructure for an electric bus fleet. The total daily cost of charging stations, degradation of electric bus batteries and consumed electricity was chosen as the objective function. The model is formulated as a mixed integer linear programming problem.Conclusion. To solve the formulated problem, standard solvers like IBM ILOG CPLEX can be used. The solution of the problem lies in the choice of durations and schedules for charging electric buses at low-capacity charging stations in the depot at night and at high-capacity charging stations of terminal stops in a given range of peak hours.Цели. При переходе от парка дизельных автобусов к парку электробусов актуальной является оптимизация зарядной инфраструктуры, совмещающей технологии медленной зарядки батарей в депо в ночное время и быстрой подзарядки на конечных остановках маршрутов. Цель исследования заключается в создании моделей и методов выработки экономически эффективных решений по выбору зарядной инфраструктуры такого типа для парка электробусов, обслуживающих систему городских маршрутов с учетом ряда специфических условий. Функционирование парка и зарядной инфраструктуры моделируется как для депо в ночной период, так и для конечных остановок в наиболее представительный период дня, характеризующийся наибольшей интенсивностью пассажиропотока и максимальным расходом электроэнергии.Методы. Используются методы теории множеств, теории графов и линейной аппроксимации.Результаты. Разработана математическая модель задачи оптимизации зарядной инфраструктуры смешанного типа для парка электробусов. В качестве целевой функции выбрана суммарная дневная стоимость зарядных станций, износа батарей электробусов парка и потребленной электроэнергии. Модель сформулирована в виде задачи смешанного целочисленного линейного программирования.Заключение. Для решения сформулированной задачи целочисленного линейного программирования могут использоваться стандартные решатели типа IBM ILOG CPLEX. Решение задачи заключается в выборе длительностей и расписаний зарядки электробусов на зарядных станциях малой мощности в депо в ночное время и на зарядных станциях большой мощности конечных остановок в заданном диапазоне часов пик

Подход к оптимизации зарядной инфраструктуры автономных троллейбусов для городских маршрутов

P u r p o s e s.  When designing a system of urban electric transport that charges while driving, including autonomous trolleybuses with batteries of increased capacity, it is important to optimize the charging infrastructure for a fleet of such vehicles. The charging infrastructure of the dedicated routes consists of overhead wire sections along the routes and stationary charging stations of a given type at the terminal stops of the routes. It is designed to ensure the movement of trolleybuses and restore the charge of their batteries, consumed in the sections of autonomous running.The aim of the study is to create models and methods for developing cost-effective solutions for charging infrastructure, ensuring the functioning of the autonomous trolleybus fleet, respecting a number of specific conditions. Conditions include ensuring a specified range of autonomous trolleybus running at a given rate of energy consumption on routes, a guaranteed service life of their batteries, as well as preventing the discharge of batteries below a critical level under various operating modes during their service life.M e t ho d s. Methods of set theory, graph theory and linear approximation are used.Re s u l t s. A mathematical model has been developed for the optimization problem of the charging infrastructure of the autonomous trolleybus fleet. The total reduced annual costs for the charging infrastructure are selected as the objective function. The model is formulated as a mathematical programming problem with a quadratic objective function and linear constraints.Co n c l u s i o n. To solve the formulated problem of mathematical programming, standard solvers such as IBM ILOG CPLEX can be used, as well as, taking into account its computational complexity, the heuristic method of "swarm of particles".  The solution to the problem is to select the configuration of the location of the overhead wire sections on the routes and the durations of charging the trolleybuses at the terminal stops, which determine the corresponding number of stationary charging stations at these stops.Ц е л и. При проектировании системы городского электротранспорта, заряжающегося во время движения, в том числе автономных троллейбусов с батареями увеличенной емкости, актуальной является оптимизация зарядной инфраструктуры для парка такого транспорта. Зарядная инфраструктура выделенных маршрутов состоит из секций контактной сети вдоль маршрутов и стационарных зарядных станций заданного типа на конечных остановках маршрутов. Она предназначена для обеспечения движения троллейбусов и восстановления заряда их батарей, израсходованного на участках автономного хода.Цель исследования заключается в создании моделей и методов выработки экономически эффективных решений по зарядной инфраструктуре, обеспечивающих функционирование парка автономных троллейбусов с учетом ряда специфических условий. Условия включают обеспечение заданного диапазона автономного хода троллейбусов при заданной скорости расхода энергии на маршрутах и гарантийного срока эксплуатации их батарей, а также предотвращение разряда батарей ниже критического уровня при различных режимах эксплуатации в течение срока их службы.М е то д ы. Используются методы теории множеств, теории графов и линейной аппроксимации.Р е з у л ь т а т ы.  Разработана математическая модель задачи оптимизации зарядной инфраструктуры парка автономных троллейбусов. В качестве целевой функции выбраны суммарные приведенные годовые затраты на зарядную инфраструктуру. Модель сформулирована в виде задачи математического программирования с квадратичной целевой функцией и линейными ограничениями.З а к л ю ч е н и е. Для решения сформулированной задачи математического программирования могут использоваться стандартные решатели типа IBM ILOG CPLEX, а также, с учетом ее вычислительной сложности, эвристический метод «роя частиц». Решение задачи заключается в выборе конфигурации расположения секций контактной сети на маршрутах и длительностей зарядки троллейбусов на конечных остановках, определяющих соответствующие количества стационарных зарядных станций на этих остановках

Structure and properties of oxygen-containing thin films and bulk MgB₂

A structural Auger spectroscopy study of MgB2 thin (~140 nm) oxygen-containing polycrystalline films produced by magnetron sputtering and 99% dense MgB2 bulks synthesized at 2 GPa allows us to conclude that jc of MgB2 depends to a high extent on the amount and distribution of oxygen in the material matrix. jc reached 7.8-2.7 MA/cm2 below 1T at 20 K in the films and 0.3-0.9 MA/cm2 (depending on the boron used) in the bulks. The higher jc in MgB2 thin films can be associated with finer oxygen-enriched Mg-B-O inclusions and their higher density in the film structure compared to the bulk. Calculations of the total electron density of states (DOS) in MgB2, MgB1.75O0.25, MgB1.5O0.5 and MgBO showed that all the compounds are conductors with metal-like behaviour. The DOS is even higher in MgB1.5O0 5 than in MgB2 and the binding energy is similar. So, the experimentally found presence of some dissolved oxygen in MgB2 does not contradict its high SC performance. The introduction of a high amount of oxygen into the MgB2 structure does not dramatically reduce the material\u27s Tc and allows obtaining highjc as observed in our MgB2 films and bulks

Structure and Transport Characteristics of Tunnel Junctions with Hybrid Semiconductor Barriers with Quantum Dots

We propose to realize MoRe/SiO_x(W)/MoRe hybrid junctions by using self-organization effects for the creation of quantum dots (tungsten clusters) in the semiconductor barriers consisting of a mixture of silicon and silicon oxide. Current-voltage characteristics of the MoRe/SiO_x(W)/MoRe samples have been measured in a wide voltage range from -900 to 900 mV at temperatures from 4.2 to 77 K. At low temperatures and for a comparatively small W content in the hybrid barrier, the heterostructures exhibited current-voltage curves of an unusual shape. Single or several current peaks caused by electron tunneling through the allowed states in the barrier have been observed in the transport characteristics. With increasing temperature, superconducting fluctuations in the MoRe electrodes become unimportant, and the current-voltage curve of a heterostructure follows the Ohm law. At last, we present theoretical description of the charge transport in such inhomogeneous systems with account of many-electron processes

Structure and transport characteristics of tunnel junctions with hybrid semiconductor barriers with quantum dots

We propose to realize MoRe/SiO_x(W)/MoRe hybrid junctions by using self-organization effects for the creation of quantum dots (tungsten clusters) in the semiconductor barriers consisting of a mixture of silicon and silicon oxide. Current-voltage characteristics of the MoRe/SiO_x(W)/MoRe samples have been measured in a wide voltage range from -900 to 900 mV at temperatures from 4.2 to 77 K. At low temperatures and for a comparatively small W content in the hybrid barrier, the heterostructures exhibited current-voltage curves of an unusual shape. Single or several current peaks caused by electron tunneling through the allowed states in the barrier have been observed in the transport characteristics. With increasing temperature, superconducting fluctuations in the MoRe electrodes become unimportant, and the current-voltage curve of a heterostructure follows the Ohm law. At last, we present theoretical description of the charge transport in such inhomogeneous systems with account of many-electron processes

Proximity phenomena in double-barrier structure NbZr/NbOₓ/Al/AlOy/NbZr

A tunneling structures NbZr/NbOₓ/Al/AlOy/NbZr with a thin barrier in the NbZr/NbOₓ/Al junction and 4 to 6-nm-thick Al interlayer were prepared and studied experimentally. A proximity effect between NbZr and Al through NbOₓ barrier has been observed. An electrical voltage was generated in the NbOx barrier and a coexistence of the proximity effect and applied voltage in the junction NbZr/NbOₓ/Al has been observed. This experiment could be described on the basis of a model for coherent charge transport in superconducting/normal proximity structures

Spectrum of constrained electronic states in heterostructures formed with superconductor and ferromagnetic metals

The dependence of ballistic Josephson’s current though heterostructures superconductor– ferromagnetic metal–isolator–ferromagnetic metal–superconductor (SF1–I–F2S) on the heterostructure’s parameters is calculated. The conditions, under which a significant increase in the considered Josephson’s current may be observed, are suggested

Phase-slip Events in MoRe-Si(W)-MoRe heterostructres

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