Magnetism in one-dimensional quantum dot arrays

We employ the density functional Kohn-Sham method in the local spin-density approximation to study the electronic structure and magnetism of quasi one-dimensional periodic arrays of few-electron quantum dots. At small values of the lattice constant, the single dots overlap, forming a non-magnetic quantum wire with nearly homogenous density. As the confinement perpendicular to the wire is increased, i.e. as the wire is squeezed to become more one-dimensional, it undergoes a spin-Peierls transition. Magnetism sets in as the quantum dots are placed further apart. It is determined by the electronic shell filling of the individual quantum dots. At larger values of the lattice constant, the band structure for odd numbers of electrons per dot indicates that the array could support spin-polarized transport and therefore act as a spin filter.Comment: 11 pages, 6 figure

Extreme sensitivity of the spin-splitting and 0.7 anomaly to confining potential in one-dimensional nanoelectronic devices

Quantum point contacts (QPCs) have shown promise as nanoscale spin-selective components for spintronic applications and are of fundamental interest in the study of electron many-body effects such as the 0.7 x 2e^2/h anomaly. We report on the dependence of the 1D Lande g-factor g* and 0.7 anomaly on electron density and confinement in QPCs with two different top-gate architectures. We obtain g* values up to 2.8 for the lowest 1D subband, significantly exceeding previous in-plane g-factor values in AlGaAs/GaAs QPCs, and approaching that in InGaAs/InP QPCs. We show that g* is highly sensitive to confinement potential, particularly for the lowest 1D subband. This suggests careful management of the QPC's confinement potential may enable the high g* desirable for spintronic applications without resorting to narrow-gap materials such as InAs or InSb. The 0.7 anomaly and zero-bias peak are also highly sensitive to confining potential, explaining the conflicting density dependencies of the 0.7 anomaly in the literature.Comment: 23 pages, 7 figure

Conductance anomalies and the extended Anderson model for nearly perfect quantum wires

Anomalies near the conductance threshold of nearly perfect semiconductor quantum wires are explained in terms of singlet and triplet resonances of conduction electrons with a single weakly-bound electron in the wire. This is shown to be a universal effect for a wide range of situations in which the effective single-electron confinement is weak. The robustness of this generic behavior is investigated numerically for a wide range of shapes and sizes of cylindrical wires with a bulge. The dependence on gate voltage, source-drain voltage and magnetic field is discussed within the framework of an extended Hubbard model. This model is mapped onto an extended Anderson model, which in the limit of low temperatures is expected to lead to Kondo resonance physics and pronounced many-body effects

The Low-Temperature Fate of the 0.7 Structure in a Point Contact: A Kondo-like Correlated State in an Open System

Besides the usual conductance plateaus at multiples of 2e2/h, quantum point contacts typically show an extra plateau at ~ 0.7(2e2/h), believed to arise from electron-electron interactions that prohibit the two spin channels from being simultaneously occupied. We present evidence that the disappearance of the 0.7 structure at very low temperature signals the formation of a Kondo-like correlated spin state. Evidence includes a zero-bias conductance peak that splits in a parallel field, scaling of conductance to a modified Kondo form, and consistency between peak width and the Kondo temperature

Контейнерная поточно-транспортная технология подготовки селекционного зерна

Abstract. Low-level mechanization is one of the main reasons for the high costs in selection and primary seed production. Crop breeders use transport and loading facilities for seed material transporting in an unsystematic manner. (Research purpose) Development of technology of transport support in selection and seed production, including all transport and loading processes of the delivery of grain seeds from selection combines to storage facilities using containers for seed collection, transportation, drying, and storage. (Materials and methods) The authors have described a container flowtransport technology of selection grain harvesting at the stage of primary reproduction and developed a machine complex technology and a database of harvesting and transport machines for seed collection, transportation, drying, and storage. (Results and discussion) The authors have determined the type of transport and loading means for the container method of seed harvesting, transportation and storage recommended for use in selection and seed production. There are four distinctive novelty positions of the presented type: the ability to transport containers in 2 rows; increased loading height from 2 m to 3 m; maximum operating radius reaches 3.8 m (vs. 2.7 m); increased cargo capacity – by 460 kg. (Conclusions) The authors suggest using the developed methodology to improve the technological process of harvesting, transportation and postharvest processing of seed grain, organize this process, as well as select machine parameters and technical equipment on the farms of the Central region of Russia. It has been suggested that test prototypes of containers and a loader with a container tilter should be designed and manufactured for use in primary crop processing.Реферат. Низкий уровень механизации – одна из главных причин высоких затрат в селекции и первичном семеноводстве. Селекционеры бессистемно пользуются транспортными и погрузочными средствами для перевозки семенного материала. (Цель исследования) Разработать технологию транспортного обеспечения в селекции и семеноводстве, включающую в себя все транспортно-погрузочные процессы доставки семян зерновых культур от селекционных комбайнов до хранилищ с использованием контейнера для сбора, транспортировки, сушки и хранения семян. (Материалы и методы) Описали контейнерную поточно-транспортную технологию заготовки селекционного зерна на этапе первичного размножения. Разработали машинный комплекс технологии и базу данных уборочных и транспортных машин для сбора, транспортировки, сушки и хранения семян. (Результаты и обсуждение) Определили типаж транспортных и погрузочных средств при контейнерном способе уборки, транспортирования и хранения семян, рекомендуемых для применения в селекции и семеноводстве. Отличие типажа по новизне представили четырьмя позициями: возможность перевозить контейнеры в 2 ряда; увеличение высоты погрузки с 2 до 3 м; набольший вылет стрелы достигает 3,8 м (против 2,7 м); грузоподъемность выше на 460 кг. (Выводы) Рекомендовали использовать разработанную методику для совершенствования технологического процесса уборки, транспортировки и послеуборочной обработки семенного зерна, организации этого процесса, а также выбора параметров средств и технической оснащенности в хозяйствах Центрального региона России. Предложили разработать и изготовить опытные образцы контейнеров и погрузчика с кантователем контейнеров для первичной переработки урожая

Circularly polarized electroluminescence from silicon nanostructures heavily doped with boron

The circularly polarized electroluminescence (CPEL) from silicon nanostructures which are the p-type ultra-narrow silicon quantum well (Si-QW) confined by {\delta}-barriers heavily doped with boron, 5 10^21 cm^-3, is under study as a function of temperature and excitation levels. The CPEL dependences on the forward current and temperature show the circularly polarized light emission which appears to be caused by the exciton recombination through the negative-U dipole boron centers at the Si-QW {\delta}-barriers interface

Container Flow-Transport Technology of Selection Grain Production

Abstract. Low-level mechanization is one of the main reasons for the high costs in selection and primary seed production. Crop breeders use transport and loading facilities for seed material transporting in an unsystematic manner. (Research purpose) Development of technology of transport support in selection and seed production, including all transport and loading processes of the delivery of grain seeds from selection combines to storage facilities using containers for seed collection, transportation, drying, and storage. (Materials and methods) The authors have described a container flowtransport technology of selection grain harvesting at the stage of primary reproduction and developed a machine complex technology and a database of harvesting and transport machines for seed collection, transportation, drying, and storage. (Results and discussion) The authors have determined the type of transport and loading means for the container method of seed harvesting, transportation and storage recommended for use in selection and seed production. There are four distinctive novelty positions of the presented type: the ability to transport containers in 2 rows; increased loading height from 2 m to 3 m; maximum operating radius reaches 3.8 m (vs. 2.7 m); increased cargo capacity – by 460 kg. (Conclusions) The authors suggest using the developed methodology to improve the technological process of harvesting, transportation and postharvest processing of seed grain, organize this process, as well as select machine parameters and technical equipment on the farms of the Central region of Russia. It has been suggested that test prototypes of containers and a loader with a container tilter should be designed and manufactured for use in primary crop processing