Kinds Of Junctions Research Articles

Microwave response of NbSe2 van der Waals Josephson junctions

van der Waals Josephson junctions utilize the interface between two superconducting ${\mathrm{NbSe}}_{2}$ crystal flakes as a tunnel barrier. We fabricate such junctions by a dry-transfer procedure and characterize them by electric transport experiments at various temperatures and under microwave irradiation at frequencies up to 224 GHz. We observe integer Shapiro steps in the current-voltage characteristics indicating a sinusoidal Josephson current-phase relation and the possibility to use this kind of junction even in the terahertz frequency range.

On the Role of Contrast Polarity: In Response to van der Helm's Comments.

In this work, we discussed and counter-commented van der Helm’s comments on our previous paper (Pinna and Conti, Brain Sci., 2019, 9, 149), where we demonstrated unique and relevant visual properties imparted by contrast polarity in eliciting amodal completion. The main question we addressed was: “What is the role of shape formation and perceptual organization in inducing amodal completion?” To answer this question, novel stimuli were studied through Gestalt experimental phenomenology. The results demonstrated the domination of the contrast polarity against good continuation, T-junctions, and regularity. Moreover, the limiting conditions explored revealed a new kind of junction next to the T- and Y-junctions, respectively responsible for amodal completion and tessellation. We called them I-junctions. The results were theoretically discussed in relation to the previous approaches and in the light of the phenomenal salience imparted by contrast polarity. In counter-commenting van der Helm’s comments we went into detail of his critiques and rejected all of them point-by-point. We proceeded by summarizing hypotheses and discussion of the previous work, then commenting on each critique through old and new phenomena and clarifying the meaning of our previous conclusions.

Analysis of Quantum-well Heterojunction Emitter Bipolar Transistor Design

The paper presents the analysis of Quantum-well Heterojunction Emitted Bipolar Transistor Design based on physical parameters with numerical computations. The specific objective of this work is to enhance the physical performance of the Quantum-well Heterojunction Emitted Bipolar Transistor Design in real world applications. There have been considered on the III-V compound materials like GaAs for p-type layer, AlGaAs for n-type layer and InGaAs for quantum-well layer for different kinds of junctions which were developed in HEBT structure. In this analyses, the parameters for implemented HEBT structure were evaluated to find the multi-quantum-well band diagram, operating frequency (unity beta frequency), rise time, storage delay time, fall time, minority carrier distribution, current gain variation, voltage-current characteristics and phonon control on quantum-well device. In these analyses, the physical parameters were carried out based on the experimental studies from the recent research works and many literatures. The physical parameters which used in this HEBT structure have been provided to solve the real fabrication problems by using theoretical concepts. The quantum-well device based on III-V compound materials was performed by using numerical techniques with the help of MATLAB. The simulation results confirm that the developed HEBT structure was suitable for fabricating the real devices for high performance applications.

The Limiting Case of Amodal Completion: The Phenomenal Salience and the Role of Contrast Polarity.

In this work, we demonstrated unique and relevant visual properties imparted by contrast polarity in perceptual organization and in eliciting amodal completion, which is the vivid completion of a single continuous object of the visible parts of an occluded shape despite portions of its boundary contours not actually being seen. T-junction, good continuation, and closure are considered the main principles involved according to relevant explanations of amodal completion based on the simplicity–Prägnanz principle, Helmholtz’s likelihood, and Bayesian inference. The main interest of these approaches is to explain how the occluded object is completed, what is the amodal shape, and how contours of partially visible fragments are relatable behind an occluder. Different from these perspectives, amodal completion was considered here as a visual phenomenon and not as a process, i.e., the final outcome of perceptual processes and grouping principles. Therefore, the main question we addressed through our stimuli was “What is the role of shape formation and perceptual organization in inducing amodal completion?” To answer this question, novel stimuli, similar to limiting cases and instantiae crucis, were studied through Gestalt experimental phenomenology. The results demonstrated the domination of the contrast polarity against good continuation, T-junctions, and regularity. Moreover, the limiting conditions explored revealed a new kind of junction next to the T- and Y-junctions, respectively responsible for amodal completion and tessellation. We called them I-junctions. The results were theoretically discussed in relation to the previous approaches and in the light of the phenomenal salience imparted by contrast polarity.

Unified scattering approach to Josephson current and thermal noise in BCS and topological superconducting junctions

We present a unified description of a junction between $s$-wave (BCS) superconductors and a junction between $p$-wave superconductors in a topologically nontrivial phase, which relies on a scattering state expansion. We compute Josephson current and thermal noise in the two kinds of junction and exhibit some characteristic features for a junction of two topological superconductors hosting Majorana zero-energy modes.

Spin-Singlet and Spin-Triplet Josephson Junctions for Cryogenic Memory

Due to the ever-increasing power and cooling requirements of large-scale computing and data facilities, there is a need for low-power alternatives to CMOS. One approach under consideration is superconducting computing based on single-flux-quantum logic. Unfortunately, there is not yet a low-power, high-density superconducting memory technology that is fully compatible with superconducting logic. We are working toward developing cryogenic memory based on Josephson junctions that contain two or more ferromagnetic (F) layers. Such junctions have been demonstrated to be programmable by changing the relative direction of the F layer magnetizations. There are at least two different types of such junctions: those that carry the innate spin-singlet supercurrent associated with the conventional superconducting electrodes, and those that convert spin-singlet to spin-triplet supercurrent in the middle of the device. In this letter, we compare the performance and requirements of the two kinds of junctions. Whereas the spin-singlet junctions need only two ferromagnetic layers to function, the spin-triplet junctions require at least three. In the devices demonstrated to date, the spin-singlet junctions have considerably larger critical current densities than the spin-triplet devices. On the other hand, the spin-triplet devices have less stringent constraints on the thicknesses of the F layers, which might be beneficial in large-scale manufacturing.

Ultrastructure of the coelom in the brachiopod Lingula anatina.

The organization of the coelomic system and the ultrastructure of the coelomic lining are used in phylogenetic analysis to establish the relationships between major taxa. Investigation of the anatomy and ultrastructure of the coelomic system in brachiopods, which are poorly studied, can provide answers to fundamental questions about the evolution of the coelom in coelomic bilaterians. In the current study, the organization of the coelom of the lophophore in the brachiopod Lingula anatina was investigated using semithin sectioning, 3D reconstruction, and transmission electron microscopy. The lophophore of L. anatina contains two main compartments: the preoral coelom and the lophophoral coelom. The lining of the preoral coelom consists of ciliated cells. The lophophoral coelom is subdivided into paired coelomic sacs: the large and small sinuses (= canals). The lining of the lophophoral coelom varies in structure and includes monociliate myoepithelium, alternating epithelial and myoepithelial cells, specialized peritoneum and muscle cells, and podocyte-like cells. Connections between cells of the coelomic lining are provided by adherens junctions, tight-like junctions, septate junctions, adhesive junctions, and direct cytoplasmic bridges. The structure of the coelomic lining varies greatly in both of the main stems of the Bilateria, that is, in the Protostomia and Deuterostomia. Because of this great variety, the structure of the coelomic lining cannot by itself be used in phylogenetic analysis. At the same time, the ciliated myoepithelium can be considered as the ancestral type of coelomic lining. The many different kinds of junctions between cells of the coelomic lining may help coordinate the functioning of epithelial cells and muscle cells.

Retinoschisin at 4 Å Resolution from cryo-EM: A Junctional Model of Back-to-Back Octamers for Adhesion in the Retina

The protein retinoschisin (RS1) plays an important role in cell-cell adhesion in the retina. Mutations in RS1 lead to X-linked retinoschisis (XLRS), a form of vision impairment in young males characterized by separation of inner retinal layers, among other effects. We expressed and purified RS1 and determined its structure by cryo-electron microscopy at ∼ 4 A, assisted by data from a direct detection camera. We visualize octameric rings, paired back-to-back and in register. RS1 (24 kDa) has a small N-terminal domain of unknown structure and a discoidin domain, for which crystal structures of homologs are known. The RS1 domains occupy the centers of the rings but are less clearly defined, suggesting mobility. We refined the cryo-EM structure of the discoidin rings by flexible fitting, and requiring consistency with known intramolecular and intermolecular disulfides. In the resulting model, the interfaces between subunits in a ring and between rings involve residues to which XLRS mutations have been mapped. We propose that RS1 couples adjacent cells through octamer-octamer contacts. Homotypic interactions between opposing protein assemblies are reminiscent of other kinds of junctions (e.g. gap junctions) but RS1differs in that it has no transmembrane component but must anchor to the membrane in some other way; this may perhaps involve the binding of RS1 domains to receptors.

Theoretical calculation of electron transport properties of atomic chains of (GaAs)n (n=1-4)

Electron transport properties of the (GaAs)n(n=1-4) linear atomic chains, which are sandwiched between two infinite Au(100)-33 leads, are investigated with a combination of density functional theory and non-equilibrium Greens function method from first principle. We simulate the Au-(GaAs)n-Au nanoscale junctions breaking process, optimize the geometric structures of four kinds of junctions, calculate the cohesion energies and equilibrium conductances of junctions at different distances. The calculation results show that there is a stable structure for each nanoscale junction. The average bond-lengths of Ga-As in each chain at equilibrium positions for stable structure are 0.220 nm, 0.224 nm, 0.223 nm, 0.223 nm, respectively. The corresponding equilibrium conductances are 2.328G0, 1.167G0, 0.639G0, and 1.237G0, respectively. It means that each of all the junctions has a good conductivity. We calculate the transmission spectra of the all the chains. With the increase of atomic number in the (GaAs)n (n=1-4) chains, there appears no oscillation phenomenon for the equilibrium conductance. We calculate the projected densities of states of all nanoscale junctions at equilibrium positions, and the results show that electronic transport channel is mainly contributed by the px and py orbital electrons of Ga and As atoms. In the voltage range of 0-2 V, we calculate the current-voltage characteristics of junctions at equilibrium positions. With the increase of external bias, the current increases, and the I-V curves of junctions show linear characteristics for the (GaAs)n (n=1-3) atomic chains. However, there appears a negative differential resistance phenomenon in each of the voltage ranges of 0.6-0.7 V and 0.8-0.9 V for the (GaAs)4 linear atomic chain.

The Quest for More Tolerant Rice: How High Concentrations of Iron Affect Alternative Splicing?

Rice (Oryza sativa L.) is a global staple food crop and an important model organism for plant studies. Recent reports have shown that alternative splicing is affected by many stressful conditions, suggesting its importance for the adaptation to adverse environments. Due to the little information on this subject, this study aimed to explore changes in splicing patterns that occur in response to high iron concentration in nutrient solutions. Here we quantified different kind of junctions and splicing events in the transcriptome of a relatively tolerant rice cultivar BRS Querencia, under iron excess with concentration of 300 mg L-1 Fe+2. Plants kept under standard conditions (control) presented 127,781 different splicing junctions, while stressed plants had 123,682 different junctions. Canonical (98.85% and 98.91%), semi-canonical (0.73% and 0.70%) and non-canonical (0.42% and 0.40%) junctions were found in control and stressed plants, respectively. Intron retention was the most frequent event (44.1% and 47.4%), followed by 3’ splice site (22.6% and 21.9%), exon skipping (18.9% and 17.3%) and alternative 5’ splice site (14.4% and 13.4%) in control and stressed plants, respectively. We also found 25 differentially expressed genes (five up and 20 down regulated) that are related to post-translational modifications. These results represent an important step in the understanding of how plant stress responses occur in an iron tolerant genotype, uncovering novel genes involved in iron stress response.

Stability of Single- and Few-Molecule Junctions of Conjugated Diamines

We study the stability of molecular junctions based on an oligo(phenylenethynylene) (OPE) diamine using a scanning tunneling microscope at room temperature. In our analysis, we were able to differentiate between junctions most probably formed by either one or several molecules. Varying the stretching rate of the junctions between 0.1 and 100 nm/s, we observe practically no variation of the length over which both kinds of junction can be stretched before rupture. This is in contrast with previously reported results for similar compounds. Our results suggest that, over the studied speed range, the junction breakage is caused purely by the growth of the gap between the gold electrodes and the elastic limit of the amine-gold bond. On the other hand, without stretching, junctions would survive for periods of time longer than our maximum measurement time (at least 10 s for multiple-molecule junctions) and can be considered, hence, very stable.

ISS2011 Development of iron-based superconducting devices

For the investigation of the superconducting properties of iron-based superconductors Josephson junctions as well as Andreev reflection studies are potential tools. Therefore, we prepared different kinds of junctions, based on transport in direction of c-axis and ab-plane, respectively. The first one was a planar hybrid superconductor-normal metal-superconductor (SNS’) thin film junction for transport studies along the c-axis. We used a BaFe1.8Co0.2As2 (Ba-122) thin film (thickness ≈ 80 nm) prepared by pulsed laser deposition (PLD) as base electrode and a lead indium alloy as counter electrode, while the normal metal (barrier) layer was formed by thin gold films. By tuning the thickness of the gold layer and the area of the tunneling window, we were able to switch the behavior of our junction. For a thin gold layer (≈ 5 nm) and greater areas, RCSJ-like Josephson behavior can be observed with a radiation dependent excess current and nearly linear temperature dependence of the critical current. Increasing the thickness of the gold layer to 10 nm leads to conductance spectra, which are dominated by Andreev reflection and which show no remaining sign of Josephson effects. Secondly, an edge-type junction for transport measurements in the ab-plane of the pnictide layer, was prepared. It also is realized with PbIn as counter electrode, but with no artificial thin film. The temperature dependent conductance spectra showed some interesting features, which cannot be described within usual theoretical models. We introduced a third geometry, phase-sensitive corner junctions, which could ultimately test the pairing symmetry of Ba-122, if it is s± type.

Charge and spin transport through a ferromagnet/insulator/unconventional superconductor junction

We analyze the charge and spin transport through a ballistic ferromagnet/insulator/superconductor junction by means of the Bogoliubov-de Gennes equations. For the ferromagnetic side we assume that ferromagnetism may be driven by an unequal mass renormalization of oppositely polarized carriers, i.e. a spin bandwidth asymmetry, and/or by a rigid splitting of up-and down-spin electron bands, as in a standard Stoner ferromagnet, whereas the superconducting side is assumed to exhibit a d-wave symmetry of the order parameter, which can be pure or accompanied by a minority component breaking time-reversal symmetry. Several remarkable features in the charge conductance arise in this kind of junction, providing useful information about the mechanism of ferromagnetism in the ferromagnetic electrode, as well as of the order parameter symmetry in the superconducting one. In particular, we show that when a time-reversal symmetry breaking superconductor is considered, the use of the two kinds of ferromagnet mentioned above represents a valuable tool to discriminate between the different superconducting mixed states. We also explain how this junction may mimic a switch able to turn on and off a spin current, leaving the charge conductance unchanged, and we show that for a wide range of insulating barrier strengths, a spin bandwidth asymmetry ferromagnet may support a spin current larger than a standard Stoner one.

Biepitaxial YBa2Cu3O7 − x 0–π Josephson junctions

We present measurements performed onYBa2Cu3O7 − x ‘0’ and‘0–π’ Josephson junctions fabricated using the biepitaxial technique withSrTiO3 as substrateand CeO2 as seed layer. Measurements of the critical current as a function of external magnetic fieldclearly show complementary behavior of the two kinds of junctions. Our resultsunambiguously show that the d-wave nature of the order parameter dominates the currenttransport across the junctions despite the faceting on the microscale along the grainboundary line.

Junctions of left‐ and right‐handed chiral carbon nanotubes – nanobamboo

AbstractSingle walled carbon nanotubes can be used as nanoscale reaction chambers for producing smaller nanotubes within the host tube from encapsulated fullerenes by annealing. The diameter of the host outer tube restricts the diameter of the inner tube due to van der Waals interactions, but not chirality; however, only a few chiralities are allowed for any given outer tube diameter. It is possible that inner tubes with different chiralities – or the same chirality but left‐ and right‐handedness– can start to grow in different places at the same time. A straight junction occurs at the connection of these two tubes. The geometry of different kinds of junctions containing pentagon and heptagon defects was optimized by density functional theory. The effect of the localized states on the electronic band structure was investigated. Geometry of our (6,4) nanobamboo from two points of view. The pentagon and heptagon defects are highlighted. magnified image

Comparison between models for p‐n junctions parameters extraction

PurposeThe purpose of this paper is to compare different junctions' parameters extraction models.Design/methodology/approachI‐V curves of p+‐n and pwell‐n diodes were measured. Five models for parameters extraction on I‐V characteristics of diodes in an educational poly‐Si gate pwell complementary metal oxide semiconductor (CMOS) technology were applied. The junctions' areas were 30 × 30 μm for the source‐body p+‐n junction of the PMOS transistor and 220 × 250 μm for the pwell‐body junction. The diodes were sintered in forming gas (10 percent of H2) in the temperature interval of 450‐525°C for times from 30 min up to 4 h.FindingsIt was shown that the best annealing regimes are different for both kinds of junctions.Originality/valueThe paper shows that the best annealing regime for p+‐n diodes (the lowest n and I0 values) is 450°C, 30 min and for the pwell‐n diodes (the lowest I0 values) is 525°C, 60 min. So, for the different kinds of junctions in one integrated circuit, different annealings could give the best parameters and the optimization depends on the specific characteristics of the developed technology.

Mesoscopic fluctuations of the supercurrent in diffusive Josephson junctions

We study mesoscopic fluctuations and weak-localization correction to the supercurrent in Josephson junctions with coherent diffusive electron dynamics in the normal part. Two kinds of junctions are considered: a chaotic dot coupled to superconductors by tunnel barriers and a diffusive junction with transparent normal-superconducting interfaces. The amplitude of current fluctuations and the weak-localization correction to the average current are calculated as functions of the ratio between the superconducting gap and the electron dwell energy, temperature, and superconducting phase difference across the junction. Technically, fluctuations on top of the spatially inhomogeneous proximity effect in the normal region are described by the replicated version of the $\ensuremath{\sigma}$ model. For the case of diffusive junctions with transparent interfaces, the magnitude of mesoscopic fluctuations of the critical current appears to be nearly three times larger than the prediction of the previous theory, which did not take the proximity effect into account.

Kinematics, dynamics, and microstructural effects of grain boundary junctions

The impact of grain boundary junctions on the coarsening of grain boundary networks is reviewed. The various kinds of junctions are introduced, the dynamic steady state configurations are defined, and their equation of motion is derived. It is shown that a limited junction mobility can effectively hinder grain growth, in particular in fine grained materials. The theory is substantiated by computer simulations and supported by experimental results. We propose to utilize Grain Boundary Junction Engineering as an effective tool for microstructure control.

Soliton junctions in the large magnetic flux limit

We study the flux tube junctions in the limit of large magnetic flux. In this limit the flux tube becomes a wall vortex which is a wall of negligible thickness (compared to the radius of the tube) compactified on a cylinder and stabilized by the flux inside. This wall surface can also assume different shapes that correspond to soliton junctions. We can have a flux tube that ends on a wall, a flux tube that ends on a monopole and more generic configurations containing all three of them. In this paper we find the differential equations that describe the shape of the wall vortex surface for these junctions. We will restrict to the cases of cylindrical symmetry. We also solve numerically these differential equations for various kinds of junctions. We finally find an interesting relation between soliton junctions and dynamical systems.

Point-contact tunneling in low-dimensional, unconventional superconducting junctions

It was observed during recent years that, at low temperatures, certain superconducting organic compounds (like for instance ( TMTSF ) 2 - PF 6 , - ClO 4 , etc.) show upper critical fields in excess of the Pauli–Clogston paramagnetic limit; usually depending on the angular orientation of the field with respect to the crystalline axes. High critical fields constitute an indication of possible triplet-pairing superconducting phases. Unambiguous interpretation of this effect is of course difficult and independent confirmations of the unconventional pairing scenario are, therefore, desirable. A number of independent experimental checks were both proposed and some carried out. Here, we are concerned with the relevant signatures of triplet superconductivity to be found in the proposed point-contact tunneling experiments. We modify and extend previous microscopic calculations of tunneling in superconducting junctions based on a non-equilibrium Green function formalism to incorporate the case of spin-triplet pairing. We show that distinctive features are present in the I– V characteristics of different kinds of junctions, in particular, when the Zeeman effect of a magnetic field is taken into account that would permit to identify the type of pairing. We discuss the relevance of these results for the case of the above-mentioned quasi-one-dimensional organic superconductors.