Superfocusing by Nano-Shells

Recently Merlin and co-workers demonstrated, both theoretically and in the microwave range experimentally, subwavelength focusing of evanescent waves by patterned plates. The present paper extends these ideas and the design procedure to scatterers of arbitrary shapes and to the optical range of wavelengths. The analytical study is supported by numerical results. The most intriguing feature of the proposed design is that, in the framework of classical electrodynamics of continuous media, focusing can in principle be arbitrarily sharp, subject to the constraints of fabrication.Comment: 4 pages, 5 figure

Magneto-optic Kerr effect in a spin-polarized zero-moment ferrimagnet

The magneto-optical Kerr effect (MOKE) is often assumed to be proportional to the magnetisation of a magnetically ordered metallic sample; in metallic ferrimagnets with chemically distinct sublattices, such as rare-earth transition-metal alloys, it depends on the difference between the sublattice contributions. Here we show that in a highly spin polarized, fully compensated ferrimagnet, where the sublattices are chemically similar, MOKE is observed even when the net moment is strictly zero. We analyse the spectral ellipsometry and MOKE of Mn 2 Ru x Ga, and show that this behaviour is due to a highly spin-polarized conduction band dominated by one of the two manganese sublattices which creates helicity-dependent reflectivity determined by a broad Drude tail. Our findings open new prospects for studying spin dynamics in the infra-red.Comment: 7 pages, 7 figure

Reconciling the theoretical and experimental electronic structure of NbO2

Metal-insulator transition materials such as NbO2 have generated much excitement in recent years for their potential applications in computing and sensing. NbO2 has generated considerable debate over the nature of the phase transition, and the values for the band gap/band widths in the insulating phase. We present a combined theoretical and experimental study of the band gap and electronic structure of the insulating phase of NbO2. We carry out ab-initio density functional theory plus U calculations, directly determining U and J parameters for both the Nb 4d and O 2p subspaces through the recently introduced minimum-tracking linear response method. We find a fundamental bulk band gap of 0.80 eV for the full DFT+U+J theory. We also perform calculations and measurements for a (100) oriented thin film. Scanning tunnelling spectroscopy measurements show that the surface band gap varies from 0.75 eV to 1.35 eV due to an excess of oxygen in and near the surface region of the film. Slab calculations indicate metallicity localised at the surface region caused by an energy level shift consistent with a reduction in Coulomb repulsion. We demonstrate that this effect in combination with the simple, low cost DFT+U+J method can account for the band widths and p-d gap observed in X-ray photoelectron spectroscopy experiments. Overall, our results indicate the possible presence of a 2D anisotropic metallic layer at the (100) surface of NbO2.Comment: 11 pages, 5 figures, plus 3 pages of Supporting Informatio

Nonlinear Charge and Current Neutralization of an Ion Beam Pulse in a Pre-formed Plasma

The propagation of a high-current finite-length ion beam in a cold pre-formed plasma is investigated. The outcome of the calculation is the quantitative prediction of the degree of charge and current neutralization of the ion beam pulse by the background plasma. The electric magnetic fields generated by the ion beam are studied analytically for the nonlinear case where the plasma density is comparable in size with the beam density. Particle-in-cell simulations and fluid calculations of current and charge neutralization have been performed for parameters relevant to heavy ion fusion assuming long, dense beams with el >> V(subscript b)/omega(subscript b), where V(subscript b) is the beam velocity and omega subscript b is the electron plasma frequency evaluated with the ion beam density. An important conclusion is that for long, nonrelativistic ion beams, charge neutralization is, for all practical purposes, complete even for very tenuous background plasmas. As a result, the self-magnetic force dominates the electric force and the beam ions are always pinched during beam propagation in a background plasma

Application of Effective Means of Management in the Conditions of Military Operations

The system of legal support for the activities of local self-government bodies plays a decisive role in ensuring territorial development. The article analyzes the place of local self-government bodies in the system of ensuring territorial development. The analysis of the leading European experience made it possible to determine that the deregulation of territorial management processes is an effective mechanism for ensuring their development. The experience of the world’s leading countries in building legal systems for regulating the activities of local self-government bodies was analyzed. The role of local self-government bodies during political crises was defined. The lack of experience in the implementation of powers by local self-government bodies under martial law determined the need to analyze Ukrainian legislation and its practical implementation after the beginning of the full-scale military aggression of the Russian Federation against Ukraine. The analysis of the legislation made it possible to determine the place of local self-government bodies in the processes of ensuring the urgent needs of the population during the period of martial law. The analysis of the needs of the population was carried out by accumulating the results of a sociological survey among Ukrainians conducted after the start of a full-scale military invasion. Based on the assessment, a ranking matrix of the population’s requests was developed, which made it possible to form the areas of work of local self-government bodies, which are defined as priorities in the conditions of martial law. Based on the analysis, methodical recommendations are proposed to improve the regulatory and legal regulation of the activities of local self-government bodies in the conditions of martial law

Anomalous skin effect for anisotropic electron velocity distribution function

The anomalous skin effect in a plasma with a highly anisotropic electron velocity distribution function (EVDF) is very different from skin effect in a plasma with the isotropic EVDF. An analytical solution was derived for the electric field penetrated into plasma with the EVDF described as a Maxwellian with two temperatures Tx >> Tz, where x is the direction along the plasma boundary and z is the direction perpendicular to the plasma boundary. The skin layer was found to consist of two distinctive regions of width of order nTx/w and nTz/w, where nTx,z/w = (Tx,z/m)1/2 is the thermal electron velocity and w is the incident wave frequency

Crystallographic characterisation of ultra-thin, or amorphous transparent conducting oxides:the case for raman spectroscopy.

The electronic and optical properties of transparent conducting oxides (TCOs) are closely linked to their crystallographic structure on a macroscopic (grain sizes) and microscopic (bond structure) level. With the increasing drive towards using reduced film thicknesses in devices and growing interest in amorphous TCOs such as n-type InGaZnO 4 (IGZO), ZnSnO 3 (ZTO), p-type Cu x CrO 2 , or ZnRh 2 O 4 , the task of gaining in-depth knowledge on their crystal structure by conventional X-ray diffraction-based measurements are becoming increasingly difficult. We demonstrate the use of a focal shift based background subtraction technique for Raman spectroscopy specifically developed for the case of transparent thin films on amorphous substrates. Using this technique we demonstrate, for a variety of TCOs CuO, a-ZTO, ZnO:Al), how changes in local vibrational modes reflect changes in the composition of the TCO and consequently their electronic properties

Concept of forming individualization of smart village methodology using AI cognitive processes

The study examines the role of digital agriculture in rural transformation and optimization of agricultural production, especially in the context of Russia. The article discusses the application of advanced sensors for soil and fertility analysis, which helps in determining potential yields and effective fertilizer application. Digital agriculture is presented as a tool to improve efficiency and productivity in rural areas, contributing to their economic growth. In addition, the study emphasizes the importance of adequate use of data and modern technology in farming. The analyses presented are based on extensive use of statistical and mathematical methods using various Python software packages. The conclusions of the study emphasize the need to integrate digital technologies in agriculture for sustainable rural development

Unravelling the atomic and electronic structure of nanocrystals on superconducting Nb(110): Impact of the oxygen monolayer

The Niobium surface is almost always covered by a native oxide layer which greatly influences the performance of superconducting devices. Here we investigate the highly stable Niobium oxide overlayer of Nb(110), which is characterised by its distinctive nanocrystal structure as observed by scanning tunnelling microscopy (STM). Our ab-initio density functional theory (DFT) calculations show that a subtle reconstruction in the surface Niobium atoms gives rise to rows of 4-fold coordinated oxygen separated by regions of 3-fold coordinated oxygen. The 4-fold oxygen rows are determined to be the source of the nanocrystal pattern observed in STM, and the two chemical states of oxygen observed in core-level X-ray photoelectron spectroscopy (XPS) are ascribed to the 3-fold and 4-fold oxygens. Furthermore, we find excellent agreement between the DFT calculated electronic structure with scanning tunnelling spectroscopy and valence XPS measurements.Comment: 8 pages, 4 figures, plus 3 pages of Supporting Informatio