17 research outputs found
In-plane fluxon in layered superconductors with arbitrary number of layers
I derive an approximate analytic solution for the in-plane vortex (fluxon) in
layered superconductors and stacked Josephson junctions (SJJ's) with arbitrary
number of layers. The validity of the solution is verified by numerical
simulation. It is shown that in SJJ's with large number of thin layers,
phase/current and magnetic field of the fluxon are decoupled from each other.
The variation of phase/current is confined within the Josephson penetration
depth, , along the layers, while magnetic field decays at the
effective London penetration depth, . For comparison
with real high- superconducting samples, large scale numerical simulations
with up to 600 SJJ's and with in-plane length up to 4000 %, are
presented. It is shown, that the most striking feature of the fluxon is a
Josephson core, manifesting itself as a sharp peak in magnetic induction at the
fluxon center.Comment: 4 pages, 4 figures. Was presented in part at the First Euroconference
on Vortex Matter in Superconductors (Crete, September 1999
Formation of Porous ZnO Nanosystems for Potential Use in Sensor Electronics
The semiconducting ZnO is a very promising material for applications in UV light emitters, optical de-tectors, solar cells, piezoelectric transducers, transparent electronics, gas sensors etc. It is known that physical properties, and as a result areas of applications, are strongly determined by morphology and size of the material’s structural elements. Therefore, the development of a technology that allows formation of nanoporous metal oxide structures with a high surface to volume ratio is of great interest nowadays. The aim of this work was to develop technology for selective formation of porous ZnO nanosystems and to de-termine the relationship between morphological characteristics of the layers obtained and their optical and electrical sensor properties with the aim of potential applications in optoelectronics and sensor electronics.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3519
Formation of Porous ZnO Nanosystems for Potential Use in Sensor Electronics
The semiconducting ZnO is a very promising material for applications in UV light emitters, optical de-tectors, solar cells, piezoelectric transducers, transparent electronics, gas sensors etc. It is known that physical properties, and as a result areas of applications, are strongly determined by morphology and size of the material’s structural elements. Therefore, the development of a technology that allows formation of nanoporous metal oxide structures with a high surface to volume ratio is of great interest nowadays. The aim of this work was to develop technology for selective formation of porous ZnO nanosystems and to de-termine the relationship between morphological characteristics of the layers obtained and their optical and electrical sensor properties with the aim of potential applications in optoelectronics and sensor electronics.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3519
Magnetic field dependence of the critical current in stacked Josephson junctions. Evidence for fluxon modes in Bi2Sr2CaCu2O8+x mesas
Modulation of the critical current across layers, Ic(H), of stacked Josephson
junctions (SJJs) as a function of an applied magnetic field parallel to the
junction planes is studied theoretically and experimentally for different
junction lengths and coupling parameters. It is shown that the Ic(H) patterns
of long SJJs are very complicated without periodicity in H. This is due to
interaction between junctions in the stack. This, in turn, gives rise to the
existence of multiple quasi-equilibrium Josephson fluxon modes and submodes
which are different with respect to the symmetry of the phase and the fluxon
sequence in SJJs. The critical current of long SJJs is multiple valued and is
governed by switching between energetically close fluxon modes/submodes. Due to
this, the probability distribution of the critical current may become wide and
may consist of multiple maxima each representing a particular mode/submode.
Experimentally, multiple branched Ic(H) patterns and multiple maxima in the Ic
probability distribution were observed for Bi2Sr2CaCu2O8+x intrinsic SJJs,
which are in a good agreement with numerical simulations and support the idea
of having different quasi-equilibrium fluxon modes/submodes in intrinsic SJJs.Comment: 5 pages, 5 figure
Stability of Driven Josephson Vortex Lattice in Layered Superconductors Revisited
We analytically study stability of sliding lattice of Josephson vortices
driven by a transport current in the stack direction in strong in-plane
magnetic field. In contrast to recent findings we obtain that there are no
diverse configurations of stable vortex lattices, and, hence, the stable
sliding vortex lattice can not be selected by boundary conditions. We find that
only the triangular (rhombic) lattice can be stable, its stability being
limited by a critical velocity value. At higher velocities there are no simple
stable lattices with single flux line per unit cell. Oblique sliding lattices
are found to be never stable. Instability of such lattices is revealed beyond
the linear approximation in perturbations of the lattice.Comment: 11 pages, 2 figures, RevTeX 4, Submitted to Phys. Rev.
Magnetic field-induced dissipation-free state in superconducting nanostructures
A superconductor in a magnetic field acquires a finite electrical resistance caused by vortex motion. A quest to immobilize vortices and recover zero resistance at high fields made intense studies of vortex pinning one of the mainstreams of superconducting research. Yet, the decades of efforts resulted in a realization that even promising nanostructures, utilizing vortex matching, cannot withstand high vortex density at large magnetic fields. Here, we report a giant reentrance of vortex pinning induced by increasing magnetic field in a W-based nanowire and a TiN-perforated film densely populated with vortices. We find an extended range of zero resistance with vortex motion arrested by self-induced collective traps. The latter emerge due to order parameter suppression by vortices confined in narrow constrictions by surface superconductivity. Our findings show that geometric restrictions can radically change magnetic properties of superconductors and reverse detrimental effects of magnetic field
Gaussian Tunneling Model of c-Axis Twist Josephson Junctions
We calculate the critical current density for c-axis Josephson
tunneling between identical high temperature superconductors twisted an angle
about the c-axis. We model the tunneling matrix element squared as a
Gaussian in the change of wavevector q parallel to the junction, . The
obtained for the s- and extended-s-wave order parameters (OP's) are consistent
with the BiSrCaCuO data of Li {\it et al.}, but only
for strongly incoherent tunneling, . A -wave OP
is always inconsistent with the data. In addition, we show that the apparent
conventional sum rule violation observed by Basov et al. might be
understandable in terms of incoherent c-axis tunneling, provided that the OP is
not -wave.Comment: 6 pages, 6 figure
Formation of porous zinc nanosystems using direct and reverse flows of DC magnetron sputtering
The work is devoted to comparative analysis of two technological solutions for Zn nanosystems formation which have been implemented on the basis of direct-current magnetron sputtering. In the first case, conventional magnetron sputtering was used and direct flows were deposited on the substrate positioned in the front of a sputterer. In the second case, reverse flows were used and the substrate was located inside the magnetron sputterer. It has been shown experimentally, that the second technological approach gives more reproducible results as compared to the classical one. In addition, usage of the reverse flows leads to significant increase in the nanosystems deposition rates
Методы оценки личностных факторов по визуальной информации, публикуемой в социальных сетях (обзор)
The article raised the question of the relevance of the analysis of visual information published by the users of social networks. This information is used to predict the “Big Five” psychological factors. Openness to experience, conscientiousness, extraversion, agreeableness, and neuroticism are the main defined factors. It is noted that while identifying personal characteristics, domestic researchers are limited, as a rule, to text polls. On the other hand, a new information technology, based on an analysis of the color-brightness features and content of photographic and video information published on the social networks “Twitted’, “Instagram”, “Facebook”, etc., is actively developing abroad. It is vital to note that visual information is invariant to a multilingual audience, which allows to overcome language barriers and related discrepancies in translations. The article provides an overview of the works in this area, it is shown how visual information correlates with the psychological factors of the users of social networks. In turn, the factors themselves correlate well among themselves and with other important characteristics of a person related to the ability to perform intellectual work, with the state of depression, aggressiveness, etc. On the basis of the performed analysis of modern works, the article specifies the connection between visual information and factors. The study was carried out separately for each type of social networks, which is determined by the preferences of psychologists to work, as a rule, within the framework of only one network, but at the same time the closeness of the patterns found by them is traced. Based on the results of the review, a conclusion was drawn on the necessity for a combined analysis of psychological factors based on visual and textual information. The study is planned to expand in the areas of connection to the analysis of images published on the social network “VKontakte”; clarification of the correlation coefficients linking the entire set of selected factors; generalization of the results