Shape resonances in the superconducting order parameter of ultrathin nanowires

We study the shape resonance effect associated with the confined transverse superconducting modes of a cylindrical nanowire in the clean limit. Results of numerical investigations of the Bogoliubov-de Gennes equations show significant deviations of the energy gap parameter from its bulk value with a profound effect on the transition temperature. The most striking is that the size of the resonances is found to be by about order of magnitude larger than in ultrathin metallic films with the same width.Comment: 4 pages, 2 figure

Atypical BCS-BEC crossover induced by quantum-size effects

Quantum-size oscillations of the basic physical characteristics of a confined fermionic condensate are a well-known phenomenon. Its conventional understanding is based on the single-particle physics, whereby the oscillations follow the size-dependent changes in the single-particle density of states. Here we present a study of a cigar-shaped ultracold superfluid Fermi gas, which demonstrates an important many-body aspect of the quantum-size effects, overlooked previously. The many-body physics is revealed in the atypical crossover from the Bardeen-Cooper-Schrieffer (BCS) superfluid to the Bose-Einstein condensate (BEC) induced by the size quantization of the particle motion. Quantized perpendicular spectrum results in the formation of single-particle subbands (shells) so that the aggregate fermionic condensate becomes a coherent mixture of subband condensates. Each time when the lower edge of a subband crosses the chemical potential, the BCS-BEC crossover is approached in this subband, and the aggregate condensate contains both the BCS and BEC-like components.Comment: 7 pages, 5 figure

USE OF MODERN TECHNIQUE IN PREPARING THE TECHNICAL DOCUMENTATION FOR THE REGISTRATION IN THE LAND BOOK OF A PROPERTY

The paper presents the way of drawing up the cadastral documentation for the first registration in the Land Book of a property. The total station and GNSS receivers were used as topographic devices for measurements, which offered a high accuracy of the measured data and a shortening of the time spent in the field. The data processing and the elaboration of the documentation was done through specialized programs (Toposys, Autocad). As the surveying method was used the method of closed planimetric traverse supported on known coordinate points (previously determined with GNSS technology), combined with the method of polar coordinates

USE OF TOTAL STATIONS AND GNSS EQUIPMENT IN THE REALIZATION OF CADASTRE DOCUMENTATIONS FOR THE FIRST REGISTRATION IN THE LAND BOOK

The paper presents an example of the use of total stations in combination with GNSS technology in order to obtain the topo-cadastral documentation of the first registration in the Land Book of a property. The elaboration of the documentation for a building located in Craiova, Brestei Street was studied. The building is composed of urban land with the category of use courtyards on which two constructions are built, one with the residential destination and the other with the annex destination. At the basis of the elaboration of the cadastral documentation were the measurements performed with the total station Trimble 3300 and the GNSS receiver Topcon GR3

Study On Some Copper - Molybdenum Based Composite Materials Condensed from the Vapour Phase

Design features of equipment are given for realizing high-speed process of electron beam evaporation and condensation. Peculiarities of phase composition and structure of a crystallized pool (melt) on copper base are studied. Assumption was made about interrelation of structure-phase state of the melt and rate of evaporation-condensation. Specifics of surface structure and volume of condensate in different sections (before and after etching) are investigated. Technological defects, their influence on strength and ductility of the condensate at tensile test are considered. Interrelation of temperature dependence of energy of deformation activation, specifics of condensate fracture and technological defects of structure, different by origin, are studied

Metallic nanograins: spatially nonuniform pairing induced by quantum confinement

It is well-known that the formation of discrete electron levels strongly influences the pairing in metallic nanograins. Here we focus on another effect of quantum confinement in superconducting grains that was not studied previously, i.e., spatially nonuniform pairing. This effect is very significant when single-electron levels form bunches and/or a kind of shell structure: in highly symmetric grains the order parameter can exhibit variations with position by an order of magnitude. Nonuniform pairing is closely related to a quantum-confinement induced modification of the pairing-interaction matrix elements and size-dependent pinning of the chemical potential to groups of degenerate or nearly degenerate levels. For illustration we consider spherical metallic nanograins. We show that the relevant matrix elements are as a rule enhanced in the presence of quantum confinement, which favors spatial variations of the order parameter, compensating the corresponding energy cost. The size-dependent pinning of the chemical potential further increases the spatial variation of the pair condensate. The role of nonuniform pairing is smaller in less symmetric confining geometries and/or in the presence of disorder. However, it always remains of importance when the energy spacing between discrete electron levels $\delta$ is approaching the scale of the bulk gap $\Delta_B$, i.e., $\delta > 0.1$-$0.2\,\Delta_B$

The Modern State of Works in Field of Electron-Beam Technology of Melting and Evaporation of Metals and Non-Metals in a Vacuum

In developing of new processes for growing metal (composite) films, the main attention is given to controlling the metal vapour flows: through energy state of the condensing particles, their molecular composition, intensity, spatial distribution of the flow, etc. It is known that the widely accepted open-type evaporators, including quasi-closed ones, are characterized by instability of the directivity diagram of the vapour flow in time, even at constant temperature. Radiation load on the film growth surface from these sources is sometimes comparable to the energy of vapour flow condensation. Therefore, when they are used, it is quite difficult to produce reproducible film structures with controllable parameters. Particular difficulties arise at high evaporation rates, when micro-drops are usually present in the vapour flow