Symmetric Junctions Research Articles

Droplet motions directed by an expansion section in the T-junctions

The controlled motion of droplets in microfluidic chips is a preliminary requirement to realize their functions. The influence of the expansion section on the droplet motion is mainly investigated in the T-junction. The droplet dynamic characteristics are analyzed at the junction and the applicable flow rate of the expansion section is explored. The expansion section can reduce the entered length and motion time of the droplet when droplets flow into the channel with it, and finally avoid the possibility of droplet splitting. Even under a large difference of the branch flow rate, the expansion section can direct the droplet into its located channel. It is found that with the increase in continuous phase flow rate, the effect of the expansion section on the droplet motion behavior is gradually weakened until it disappears. Moreover, the critical conditions of it can be obtained by theoretical calculation. The expansion section can direct droplet motion in both symmetric and asymmetric junctions. However, it is mainly achieved by influencing the interfacial tension of the droplets in the symmetric junction, while the key force is related to the droplet motion in the asymmetric junction. Specifically, the expansion section influences the differential pressure force to direct the droplet in the flow into the side branch (with expansion section) mode, but it varies the interfacial tension of the droplet in the flow into the main branch mode.

Study of conductance in graphene nanochannels for symmetric and asymmetric junction configurations

Study of conductance in graphene nanochannels for symmetric and asymmetric junction configurations

Dual‐Polarity Response in Self‐Powered Infrared SnTe Photodetector with Double Symmetric Schottky Junctions

AbstractSelf‐powered photodetectors with dual‐polarity response have great advantages in processing complex light information that is proven to be applied in switchable light imaging, optical communication, and spectral band distinction. Here, a novel strategy for designing self‐powered photodetectors by introducing the double symmetric Schottky junctions at the semiconductor‐metal interfaces is proposed, which guarantees the linear response characteristic and dominates the transfer of photogenerated carriers without external bias. Narrow bandgap semiconductor SnTe is employed as the photosensitive material. The bandgap is characterized to be 126 meV, showing great potential for wide spectrum response. As the consequence of selective excitation of unilateral Schottky junction and switching of electric field polarity, the device obtains a dual‐polarity photoresponse, which can be tuned from −14.8 to 13.5 µV. Moreover, an ultra‐broadband photoresponse from near‐infrared 808 nm to far infrared 10.6 µm is achieved with deep exploration of the working mechanism. The synergistic effect of photo thermoelectricity and photoconductivity created a high photoresponsivity of 0.35 mV W−1 excited by 10.6 µm at room temperature. This work provides a novel design strategy for self‐powered photodetectors with a dual‐polarity powered principle, which can take full advantage of the directivity of the photoresponse to identify optical information.

Effective theory for graphene nanoribbons with junctions

Graphene nanoribbons are a promising candidate for fault-tolerant quantum electronics. In this scenario, qubits are realized by localized states that can emerge on junctions in hybrid ribbons formed by two armchair nanoribbons of different widths. We derive an effective theory based on a tight-binding ansatz for the description of hybrid nanoribbons and use it to make accurate predictions of the energy gap and nature of the localization in various hybrid nanoribbon geometries. We use quantum Monte Carlo simulations to demonstrate that the effective theory remains applicable in the presence of Hubbard interactions. We discover, in addition to the well-known localizations on junctions, which we call “Fuji”, a new type of “Kilimanjaro” localization smeared out over a segment of the hybrid ribbon. We show that Fuji localizations in hybrids of width N and N+2 armchair nanoribbons occur around symmetric junctions if and only if N(mod3)=1, while edge-aligned junctions never support strong localization. This behavior cannot be explained relying purely on the topological Z2 invariant, which has been believed to be the origin of the localizations to date. Published by the American Physical Society 2024

Electronic transport in nearly compensated half-metallic FeMnGa based-junction

The all-electron full-potential linearized augmented plane-wave method is used to investigate the structural, electronic, and magnetic properties of the cubic C1b FeMnGa. We show that FeMnGa is a spin-gapless semiconductor, and by changing the lattice constant, we obtain a nearly compensated half-metallic ferrimagnet. This makes it suitable for spintronic devices. Then, a combined non-equilibrium Green’s function and density functional theory are used to show that both symmetric and asymmetric FeMnGa/Pd/FeMnGa junctions present infinite giant magneto-resistance, with higher conductance obtained for the symmetric junction with Fe–Pd interfaces.

Enhancing electricity generation during water evaporation through a symmetric double Schottky-junction design

Extensive efforts have been made to investigate energy conversion process based on metal-semiconductor Schottky junctions. In this study we report the exploration of electricity generation through water evaporation on the surface with double Schottky junctions of symmetric design. By using such symmetric Schottky junctions at both side of a silicon wafer, the electricity generation is enhanced over the system with just a single Schottky junction. In the symmetric-junction system, water evaporation on the surface of one Schottky junction breaks the symmetry, leading to the generation of a continuous and direct current. The evaporation-induced cooling and continuous liquid-solid contact electrification at the Schottky junction on one side of the system enable the fast flow of the hot electrons across the Schottky junction on the other side. This work not only demonstrates a continuous and direct-current generation system, which has the potential of harvesting a broad range of waste heat and enabling many promising applications, but also offers a general strategy using the symmetric design of Schottky junctions to enhance electricity generation in diverse energy conversion systems.

Absence of the torcular, review of venous sinus anatomy, and the simplified dural sinus classification.

Classically, the torcular Herophili is described as the symmetric junction between the superior sagittal sinus (SSS), transverse sinuses (TSs), and straight sinus (SS). However, finding this pattern in practice is not standard. Anatomical variations are common, and different drainage patterns should be expected. Existing literature proposes highly detailed descriptions and classifications of this region. Still, a simplified and practical categorization is not available. We present an anatomical finding of the torcular Herophili discovered on a cadaveric dissection. Then, we conducted a retrospective study examining the 100 most recent cranial magnetic resonance venographies (MRVs) from the Mayo Clinic, labeling them with a new proposed dural sinus classification system. Images were initially classified by two authors and further validated by a board-certified neurosurgeon and a board-certified neuroradiologist from our institution. To measure consistency in image identification, two additional international neurosurgeons were asked to classify a subset of the same MRV images, and their answers were compared. Of the MRV cohort, 33 patients were male and 67 were female. Their ages ranged from 18 to 86years, with a mean of 47.35years and a median of 49years. Upon examination, 53 patients presented as confluent (53%), 9 as SSS divergent (9%), 25 as SS divergent (25%), 11 as circular (11%), and 2 as trifurcated (2%). The inter-rater reliability ranked very good; agreement between the two neurosurgeons was 83% (κ = 0.830, p < 0.0005). The confluence of the venous sinuses is a highly variable anatomical area that is rarely evaluated with neuroimaging before surgery. The classic textbook configuration is not the rule. Using a simplified classification system may increase awareness and hopefully patient safety by preparing the physician for anatomical variations that they will encounter in a surgical or clinical scenario.

Ground states and magnonics in orthogonally coupled symmetric all-antiferromagnetic junctions

In this paper, the rich ground-state structure of orthogonally coupled symmetric all-antiferromagnetic junctions with easy-plane anisotropy is reported. A spin reorientation process rather than the traditional spin flop (SF) occurs, resulting in a phase in which N\'eel vectors preserve the mirror-reflection symmetry (termed MRS phase). The phase transitions in the ground state between SF and MRS phases can be either first or second order. After disturbed by external stimuli, magnons with different parities emerge. For in-plane dc fields, no couplings between magnons occur. When dc fields become oblique, coherent couplings between magnons with opposite parity emerge, leading to anticrossings in resonance frequencies. However, self-hybridization among magnons with the same parity never happens. More interestingly, spin waves based on MRS phases are linearly polarized and their polarization directions can be fine controlled.

Hidden Symmetries in Acoustic Wave Systems.

Latent symmetries are hidden symmetries which become manifest by performing a reduction of a given discrete system into an effective lower-dimensional one. We show how latent symmetries can be leveraged for continuous wave setups in the form of acoustic networks. These are systematically designed to possess latent-symmetry induced pointwise amplitude parity between selected waveguide junctions for all low frequency eigenmodes. We develop a modular principle to interconnect latently symmetric networks to feature multiple latently symmetric junction pairs. By connecting such networks to a mirror symmetric subsystem, we design asymmetric setups featuring eigenmodes with domain-wise parity. Bridging the gap between discrete and continuous models, our work takes a pivotal step towards exploiting hidden geometrical symmetries in realistic wave setups.

TCAD performance analysis of a symmetrical double gate non-aligned junction FET device with high and low dielectric gate oxide in sub-100 nm regime

ABSTRACT This paper presents 2D-Sentaurus TCAD tool results of a Non-aligned Double Gate Junction N-Channel Field Effect Transistor (NADGNFET) device; the response analysis of device to gate oxide dielectric materials, i.e. silicon dioxide (SiO2) and hafnium dioxide (HfO2), is also presented. The NADGNFET in 90 nm device length is the proposal of this work to improve the second-order effects as well transistor non-linear performance at radio frequency (RF). A non-aligned device in this work consists of two gates extending to the source and drain region with 44.44% channel overlap in total device length. As compared to a full overlap device, the present device has shown better results in Analog Figure of Merit (FOM) and RF parameters like: ION current, ION/IOFF ratio, DIBL (Drain Induced Barrier lowering), SS (Subthreshold Swing), Intrinsic gain (AVO), Transconductance Generation Factor (TGF), Transconductance Frequency Product (TFP), Cut-off frequency (fT), Intercepted Input Power-3 (IIP3) and Intermodulation Distortion power-3 (IMD3). The use of dielectric material with high dielectric constant (HfO2, k = 24) in gate oxide reduces DIBL by 50%, increases the ION/IOFF ratio by 59.1%, increases the Intrinsic gain by 50% compared to low-k dielectric constant (SiO2, k = 3.9). However, results also shows that high-frequency parameters’ results were better with low-k dielectric constant. This gives a trade-off in device application.

Thermoelectric Response Enhanced by Surface/Edge States in Physical Nanogaps.

Current solid-state thermoelectric converters have poor performance, which typically renders them useless for practical applications. This problem is evidenced by the small figures of merit of typical thermoelectric materials, which tend to be much smaller than 1. Increasing this parameter is then key for the development of functional devices in technologically viable applications that can work optimally. We propose here a feasible and effective design of new thermoelectric systems based on physical gaps in nanoscale junctions. We show that, depending on the type of features, i.e., the character of surface/edge states, on both sides of the gap, it is possible to achieve high figures of merit. In particular, we show that, for configurations that have localized states at the surfaces/edges, which translate into sharp resonances in the transmission, it is possible to achieve large Seebeck coefficients and figures of merit by carefully tuning their energy and their coupling to other states. We calculate the thermoelectric coefficients as a function of different parameters and find non-obvious behaviors, such as the existence of a certain coupling between the localized and bulk states for which these quantities have a maximum. The highest Seebeck coefficients and figures of merit are achieved for symmetric junctions, which have the same coupling between the localized state and the bulk states on both sides of the gap. The features and trends of the thermoelectric properties and their changes with various parameters that we find here can be applied not only to systems with nanogaps but also to many other nanoscale junctions, such as those that have surface states or states localized near the contacts between the nanoscale object and the electrodes. The model presented here can, therefore, be used to characterize and predict the thermoelectric properties of many different nanoscale junctions and can also serve as a guide for studying other systems. These results pave the way for the design and fabrication of stable next-generation thermoelectric devices with robust features and improved performance.

EFFECT OF GLYCOLYSIS SUPRESSION ON ULTRASTRUCTURE OF THE HIPPOCAMPAL GIANT SYNAPSES

Suppression of glycolysis in the rat hippocampal formations was induced by daily intracerebroventricular injection of 2-deoxy-D-glucose for 10 days. Using electron microscopy, a disturbance of morphological interactions of axonal terminals of granular neurons with perisynaptic astrocytic processes was found. At the same time, both the determinant ultrastructural characteristics of giant synapses and two types of functional contacts (asymmetric chemical active zones with dendritic spines and symmetric adhesive junctions with dendrites) were retained. However, they showed morphological signs of a weakening of synaptic processes, which were expressed in a decrease in the number of intraterminal active zones, clustering of synaptic vesicles, and their removal from neurotransmitter release sites. Compared to the norm, an increase in the number of small mitochondria with an electron-dense matrix and the evidence of initiation of glycogen synthesis in the form of glycosomes were found in the giant terminals. The data obtained indicate that the giant synapses of the hippocampal mossy fibers are a plastic, self-correcting system that is able to function by adapting its own bioenergetic metabolism, when brain glycolysis is suppressed.

Ultradense One-Memristor Ternary-Content-Addressable Memory Based on Ferroelectric Diodes

In this Letter, for the first time, one-memristor (1M)-based ternary-content-addressable memory (TCAM) with an ultradense 4F2 cell area is proposed on a single reconfigurable TiN/hafnium zirconium oxide (HZO)/indium gallium zinc oxide (IGZO)/TiN ferroelectric (FE) diode. By modulating the FE-polarization-controlled Schottky junction that exists at the interface, reconfigured P–N, N–P, and ohmic like junctions of the FE diodes were designed for ‘0’, ‘1’, and ‘X’ storage states in the TCAM cell, respectively. In addition to non-volatile FE polarization for data storage, ambipolar-like behavior induced by the symmetrical junction characteristics was obtained on the diodes for searching queries. Using both non-volatile and ambipolar-like characteristics, typical TCAM functions with a maximum driving on/off ratio of ~500 were confirmed experimentally on a single FE diode, indicating the great potential of this memory device in area-efficient artificial intelligence processors.

Electrochemically controlled rectification in symmetric single-molecule junctions

Single-molecule electrochemical science has advanced over the past decades and now extends well beyond molecular imaging, to molecular electronics functions such as rectification and amplification. Rectification is conceptually the simplest but has involved mostly challenging chemical synthesis of asymmetric molecular structures or asymmetric materials and geometry of the two enclosing electrodes. Here we propose an experimental and theoretical strategy for building and tuning in situ (in operando) rectification in two symmetric molecular structures in electrochemical environment. The molecules were designed to conduct electronically via either their lowest unoccupied molecular orbital (LUMO; electron transfer) or highest occupied molecular orbital (HOMO; "hole transfer"). We used a bipotentiostat to control separately the electrochemical potential of the tip and substrate electrodes of an electrochemical scanning tunneling microscope (EC-STM), which leads to independent energy alignment of the STM tip, the molecule, and the STM substrate. By creating an asymmetric energy alignment, we observed single-molecule rectification of each molecule within a voltage range of ±0.5 V. By varying both the dominating charge transporting LUMO or HOMO energy and the electrolyte concentration, we achieved tuning of the polarity as well as the amplitude of the rectification. We have extended an earlier proposed theory that predicts electrolyte-controlled rectification to rationalize all the observed in situ rectification features and found excellent agreement between theory and experiments. Our study thus offers a way toward building controllable single-molecule rectifying devices without involving asymmetric molecular structures.

Temperature-Biased Double-Loop Josephson Flux Transducer

We theoretically study the behavior of the critical current of a thermally-biased tunnel Josephson junction with a particular design, in which the electrodes of the junction are enclosed in two different superconducting loops pierced by independent magnetic fluxes. In this setup, the superconducting gaps can be modified independently through the magnetic fluxes threading the loops. We investigate the response of the device as a function of the magnetic fluxes, by changing the asymmetry parameter, i.e., the ratio between the zero-temperature superconducting gaps $\delta=\Delta_{10}/\Delta_{20}$, and the temperatures of the two rings. We demonstrate a magnetically controllable step-like response of the critical current, which emerges even in a symmetric junction, $\delta=1$. Finally, we discuss the optimal working conditions and the high response of the critical current to small changes in the magnetic flux, reporting good performances of the transducer, with a high transfer function that depends on the operating point and the quality of the junction.

Multiband superconductivity in SrFe2−xNixAs2

In this paper, we present a detailed study of the upper critical field and the energy gap structure of SrFe2−xNixAs2 single crystals with different nickel doping levels. Superconducting transitions were measured resistively in longitudinal and transverse magnetic fields up to 16T. The anisotropy of the upper critical field Hc2||ab/Hc2||c decreases monotonically to 1.4 with decreasing temperature for all measured samples. The WHH model was not able to fit measured Hc2(T) temperature dependences well, but the effective two-band model is in good agreement with the data and anisotropy behavior. Values and temperature dependences of superconducting gaps were determined directly by multiple Andreev reflection spectroscopy on symmetrical SnS junctions. Andreev reflections study revealed two superconducting gaps; our data are in line with the experimental results on most iron-based superconductors.Article highlightsWe obtained values and temperature dependencies of two distinct energy gaps in SrFe2−xNixAs2 (Sr-122) superconductor. This is important addition to multiband superconductivity studies in Sr-122 system. Upper critical field temperature dependencies in H||c and H||ab orientations are analyzed in terms of two band model.

Comparative study of symmetrical and asymmetrical B40 molecular junctions

This work investigates quantum transport in symmetrical and asymmetrical borospherene-based molecular junctions with adenine. Adenine is one of the four nucleobases of DNA and was selected because of its excellent transport properties. The density functional/non-equilibrium Green's function (DFT-NEGF) mathematical approach was utilized, which was further used to calculate quantum transport parameters including the I–V curve, transmission spectra, highest occupied molecular orbital (HOMO)–lowest occupied molecular orbital (LUMO) gap (HLG), differential conductance, and transmission pathways. We observed that both symmetrical and asymmetrical devices exhibit nonlinear behavior, thus leading to non-differential resistance. Also, the symmetrical B40 molecular device demonstrated reduced HLG relative to the asymmetrical B40 molecular device. This drop in HLG was due to a reduction in electron density. A high rectification ratio for the devices was observed at 0.2 V. Hence, symmetrical and asymmetrical B40 molecular junctions are potential candidates for use in future nanoscale devices.

Negative tension controls stability and structure of intermediate filament networks

Networks, whose junctions are free to move along the edges, such as two-dimensional soap froths and membrane tubular networks of endoplasmic reticulum are intrinsically unstable. This instability is a result of a positive tension applied to the network elements. A paradigm of networks exhibiting stable polygonal configurations in spite of the junction mobility, are networks formed by bundles of Keratin Intermediate Filaments (KIFs) in live cells. A unique feature of KIF networks is a, hypothetically, negative tension generated in the network bundles due to an exchange of material between the network and an effective reservoir of unbundled filaments. Here we analyze the structure and stability of two-dimensional networks with mobile three-way junctions subject to negative tension. First, we analytically examine a simplified case of hexagonal networks with symmetric junctions and demonstrate that, indeed, a negative tension is mandatory for the network stability. Another factor contributing to the network stability is the junction elastic resistance to deviations from the symmetric state. We derive an equation for the optimal density of such networks resulting from an interplay between the tension and the junction energy. We describe a configurational degeneration of the optimal energy state of the network. Further, we analyze by numerical simulations the energy of randomly generated networks with, generally, asymmetric junctions, and demonstrate that the global minimum of the network energy corresponds to the irregular configurations.

The relaxed area of 𝕊1-valued singular maps in the strictBV-convergence

Given a bounded open set Ω ⊂ ℝ2, we study the relaxation of the nonparametric area functional in the strict topology inBV(Ω; ℝ2). and compute it for vortex-type maps, and more generally for maps inW1,1(Ω;S1) having a finite number of topological singularities. We also extend the analysis to some specific piecewise constant maps inBV(Ω;S1), including the symmetric triple junction map.

Roles of triple and quadruple junctions on plasticity by phase-field crystal approach

Roles of non-/symmetric triple and quadruple junctions on plasticity of ploycrystals are examined using phase-filed crystal model combined with an isovolumetric deformation technique. We designed four polycrystalline samples containing the four types of junctions respectively to simulate the deformation process under a strain rate comparable to practical situations. Our results uncover relationships between the ability of resistances to external deformations and the deformation mechanisms. For the ploycrystals containing quadruple junctions, the symmetric junction is beneficial to maintain the stability of the junctions during deformations, while asymmetric ones would be disjointed and result in formation and growth of sub-grains. For the polycrystals containing triple junctions, the stability of the junction is strongly related to the misorientation angles of the associated grains. The triple junction composed with high-angle GBs exhibits excellent stability under successive deformations and the deformation is dominated by GB migrations. Low-angle GBs migrate more easily than the high-angle ones.