Tunneling Effect Research Articles

Analysis of tunneling effect in different structures of one-dimensional barriers

Through the construction of mathematical model and the derivation of quantum mechanics formula, transmission coefficients of different one-dimensional barrier are explored. The difference of transmission coefficient and other properties under different materials was studied by controlling the change amount in the experiment. This study focuses on the analysis of one-dimensional barrier transmission coefficients of triangles and trapezoids, and ensures the accuracy of the experimental process through a large number of literature analysis. On this basis, the study of quantum tunneling effect should be easier, and it will be applied to more fields, which will play a crucial role for further research in the future. The special point of this experiment is to analyze and compare the transmission coefficient of different forms of one-dimensional barrier, compare the theoretical value with the actual value, and correct.The purpose of this experiment is to re-examine the original inherent conclusions and add new ones, so as to keep pace with the time.

The quantum tunnelling effect in double barrier structure

The purpose of this paper is to study the quantum tunnelling effect of double barriers. At the beginning, the research background and application of quantum tunnelling effect are described, and then the research purpose is explained. Although the real double barriers are very complex, most of them are composed of double barrier, double triangle barrier and double parabola barrier. The author mainly studies the barrier of double parabola. The reason is that the quantum tunnelling effect proposed by Hund will greatly adjust the internal structure of triangular conical molecules, which has great research significance. In triangular conical molecules, the change of potential energy of a single atom with its position may be very complicated, but the part that can occur with the consequential effect is similar to the potential barrier of a double parabola. In this paper, the wave function, projection and reflection coefficients of the biparabolic barrier tunnelling effect are analysed to determine whether it has a great adjustment effect on triangular conical molecules.

The discussion of the transmission coefficient of one-dimensional double barrier

Quantum theory plays a significant part in the modern physics and makes modern technology rapidly developed. Quantum tunnel effect is one of the most important discoveries. The exact expression of potential barrier is tough to derive, even for the double barrier. Many researchers have analysed the applications of quantum tunnel effect in real electronic devices. However, the exact expression of double barriers transmission coefficient was discussed rarely. In this article, the exact expression of the transmission coefficient will be given and the effect of parameters of barrier such as the width and the height will be discussed. In addition, the difference between symmetric and asymmetric double barrier will be given. This paper has the discussion of the transmission coefficient in order to not only give a clear understanding of the effect of parameters of double barrier to tyro and researchers, but also give a simpler way to consider the periodic barrier.

Transmission coefficient in double barrier quantum tunnelling effect

At the turn of the twentieth century, the establishment of quantum theory propelled rapid advancements, particularly in the understanding of quantum tunnellinga fundamental phenomenon in quantum mechanics crucial for various physical processes. The quantum phenomenon of particle passes through potential barriers is of great importance. In classical physics, when the energy of a particle is less than the height of a double barrier structure, it is impossible for it to pass through. However, quantum mechanics allows a particle to penetrate the barrier and emerge on the other side. This paper explores the quantum tunnelling effect, focusing on the single potential barrier model in one dimension and subsequently extending to the double potential barrier model. The Schrdinger equation provides the foundational framework for elucidating the motion of microscopic particles, emphasizing wave-particle duality inherent in quantum mechanics. The analysis of the single potential barrier model involves solving the Schrdinger equation in different regions, determining wave functions and coefficients through boundary conditions. The transmission coefficient is derived, representing the probability of a particle passing through a barrier. In the case of a thick barrier, an approximate form for transmission coefficient is provided, demonstrating the exponential decrease in transmission probability with increasing barrier thickness.

Tunable Epsilon‐and‐Mu‐Near‐Zero Metacomposites

AbstractEpsilon‐and‐mu‐near‐zero (EMNZ) metamaterials have garnered significant attention in near‐zero‐parameter metamaterial research for their exceptional ability to attain concurrent near‐zero permittivity and permeability. Nowadays achieving EMNZ properties through the use of metacomposites remains a novel endeavor. Presented here is an innovative approach of near‐zero‐parameter metacomposites, illustrating excellent and tunable EMNZ properties in the radio frequency regime. The self‐organization approach is applied to construct the conductive 3D network and the circuits, serving as the underlying framework for achieving EMNZ properties. Near‐zero permeability is effectively maintained while permittivity reaches epsilon‐near‐zero frequency regime. Efficient manipulation of electromagnetic parameters is initially realized via adjusting component content in metacomposites. Significantly, an excellent EMNZ property is observed as carbon content reaches 15 wt.% at 915 MHz. Through both numerical simulations and experimental testing, the PGC metacomposites have exhibited tunneling effects and directional emission characteristics, confirming their EMNZ properties. Besides, the Lego‐like adjustment facilitates the achievement of EMNZ property and advances the EMNZ frequency point to 700 MHz, expanding the EMNZ range. Furthermore, thanks to the remarkable excitation effect of photo‐induced adjustment, the metacomposite with low‐carbon content also achieves extraordinary EMNZ properties. This research offers promising self‐organized EMNZ metacomposites and lays the foundation for future endeavors in precisely adjusting near‐zero parameters.

Statistical Model of Hydrogen Diffusion in BCC Metals

The purpose of this work is developing of the statistical model of hydrogen diffusion in the crystal lattice of BCC metals with an estimate of the contribution of quantum effects and deviations from the Arrhenius equation. The values of the statistical model calculations of H diffusion coefficients in Fe, V, Nb and Ta are in good agreement with the experimental data. The statistical model can also explain deviations from the Arrhenius equation at temperatures 300-500 K in Fe and Nb. The downward deviation of the diffusion coefficient at 300K can be explained by the fact that the statistical model does not consider the tunneling effect at temperatures below 300K. It was suggested that thermally activated fast tunnelling transition of hydrogen atoms through the potential barrier at temperatures below 500 K provides an almost free movement of H atoms in the α-Fe and V. Using the statistical model allows for the prediction of the diffusion coefficient for H in BCC metals at intermediate temperatures.

Hydrogen Tunneling in Stoichiometric and Catalytic Reactions involving Transition Metals

AbstractHydrogen tunneling is a type of quantum tunneling in which a hydrogen atom passes through a potential barrier without reaching the transition state governed by classical mechanics. The participation of hydrogen tunneling in a chemical reaction (stoichiometric or catalytic) can result in the formation of products that without this phenomenon would be impossible to achieve or would be formed in a very slow way. This concept paper aims to review some of the most representative examples of transition‐metal mediated chemical reactions involving hydrogen tunneling. The experimental tools to determine the possibility of the participation of quantum tunneling in a chemical reaction are presented. In addition, the theoretical methods that have been developed to calculate the effect of quantum tunneling on chemical reactions are discussed. Finally, from a personal perspective, the steps to be taken in order to predict and implement this phenomenon are proposed.

Photonic Spin Hall Effect as a Highly Sensitive Refractive Index Sensing Platform for Glucose

AbstractThis study presents an innovative refractive index (RI) sensor that measures glucose concentration by utilizing the photonic spin Hall effect (SHE) in a resonant optical tunneling effect (ROTE) structure. The ROTE structure consists of three InP layers with the high RI and two analyte layers (with a high‐low‐high‐low‐high RI distribution), in which glucose solution samples with the low RI are injected. By subjecting the InP layers to external bias‐assisted light, the photonic SHE can be flexibly manipulated, enabling the modulation of the sensing performance accordingly. It is found that the transverse shift of photonic SHE presents a large variation in response to the tiny change in glucose concentrations. By optimizing the parameters (i.e., intensity or wavelength) of bias light, the sensitivity of this sensor can reach as high as 735.7 µm RIU−1. Compared to traditional glucose sensors, this original work implements the novel photonic SHE with the superior sensing performance. Therefore, the proposed design shows promising potential for biomedical applications, such as medical diagnoses and drug discovery.

Theoretical Kinetic Study on Hydrogen Abstraction Reactions from n-Pentane by NO2.

The interaction of fuel with NOx chemistry is important for the construction of the reaction mechanism and engine application. In this work, the reaction pathways of nC5H12 + NO2 were studied by high-level electronic structure calculations (DLPNO-CCSD(T)-F12/cc-pVTZ-F12//B2PLYPD3/cc-pVTZ). The rate constants were calculated by using the multistructural canonical transition-state theory with the Eckart tunneling method (TST/MS-T/ET). The studied condition is in a wide temperature range of 298-2400 K. The influence of MS-T anharmonicity and tunneling effect will be clarified for these site-specific H-abstraction pathways. The result reflects the large deviation introduced by the treatment of MS-T anharmonicity, especially at a high temperature. For the same type of reactions, the rate constants of H-abstraction both occurring at the secondary carbon are not almost identical. The branching ratios show that abstraction from the secondary site forming cis-HONO (R2c) contributes 36-78% to nC5H12 consumption in the temperature range of 298-2400 K. The current results show that the multistructural torsional anharmonicity has a crucial influence on the accurate estimation of branching ratios.

Efficient vacuum pair production in frequency chirped electric fields with spatiotemporal inhomogeneity

Vacuum pair production under intense electromagnetic fields is an intriguing prediction in quantum electrodynamics (QED), and has become a topic of considerable interest with the rapid advancements in laser technologies. The pair production efficiency can be enhanced using chirped electric fields. In this study, the effects of electric field chirping on electron–positron pair production in different oscillating electric fields were investigated using the Dirac–Heisenberg–Wigner (DHW) formalism. We primarily considered quadratic and sinusoidal chirped electric fields. The results revealed that chirping significantly influences the momentum spectra of the generated particles in an electric field dominated by low-frequency tunneling effects, resulting in pronounced oscillations of the momentum spectrum, particularly in a sinusoidal chirped field. However, multiphoton processes gradually emerge as the chirp parameter increases. Consequently, in a high-frequency electric field dominated by multiphoton processes, the number density of the generated particles increases with the chirping parameter in a quadratic chirped field, whereas the momentum distribution remains relatively symmetric. However, in a sinusoidal chirped electric field, introducing a chirp parameter immediately alters the momentum distribution and enhances pair production rate. Moreover, there exists an optimal chirp parameter and the total particle number is enhanced approximately more than an order of magnitude with optimal chirping in a sinusoidal chirped electric field. These findings provide valuable insights into the intricate dynamics of pair production under the influence of chirping in different oscillating electric fields, and offer potential directions for future research in this domain.

Mitigating Raman relaxation for high-temperature single-molecule magnets

Previous studies on how to prolong the relaxation times of single-molecule magnets (SMMs) focus on mitigating the quantum tunneling effect. However, recent progress shows that Raman relaxation is more critical. Yet, the study of the Raman process turns out to be a barren zone for molecular systems and requires further exploration.

Thermo-Mechanical and Mechano-Thermal Effects in Liquids Explained by Means of the Dual Model of Liquids

We pursue to illustrate the capabilities of the Dual Model of Liquids (DML) showing that it may explain crossed effects notable in Non-Equilibrium Thermodynamics (NET). The aim of the paper is to demonstrate that the DML may correctly model the thermodiffusion, in particular getting formal expressions for positive and negative Soret coefficient, and another “unexpected” mechano-thermal effect recently discovered in liquids submitted to shear strain, for which the first-ever theoretical interpretation is provided. Both applications of the DML are supported by the comparison with experimental data. The phenomenology of liquids, either pure or mixtures, submitted to external force fields is characterized by coupled effects, for instance mechano-thermal and thermo-mechanical effects, depending on whether the application of a mechanical force field generates a coupled thermal effect in the liquid sample or vice-versa. Although these phenomena have been studied since their discoveries, dating back to the XIX century, no firm theoretical interpretation exists yet. Very recently the mesoscopic model of liquids DML has been proposed and its validity and applicability demonstrated in several cases. According to DML, liquids are arranged on a mesoscopic scale by means of aggregates of molecules, or liquid particles. These structures share the liquid world with a population of lattice particles, i.e., elastic waves that interact with the liquid particles by means of an inertial force, allowing the mutual exchange of energy and momentum between the two populations. The hit particle relaxes the acquired energy and momentum due to the interaction, giving them back to the system a step forward and a time-lapse later, alike in a tunnel effect.

Piezoresistive Theory and Numerical Calculation for Carbon Nanotube Polymer Composite.

A three-dimensional theory has been established for the piezoresistivity of carbon nanotube (CNT) polymer composites. Based on the Mori-Tanaka method in meso-mechanics theory and considering quantum tunneling effect between CNTs, an approach to calculate equivalent electrical conductivity of composites was proposed. On this basis, a piezoresistive theory, which incorporates the effect of composites' geometric nonlinearity, was developed for CNT polymer composites. The theory is dependent only on some basic physical parameters of the materials. A finite element formula of the theory for the numerical calculation of piezoresistivity was presented from the analysis of both elastic and electric fields. Numerical simulations demonstrated that the results predicted by the theory were in good agreement with those of the experimental tests. Parameter sensitivity analysis revealed that when both the potential barrier height of the matrix and the initial average separation distance between CNTs increased, the piezoresistivity obviously increased. However, with the increase in aspect ratio and CNT conductivity, the piezoresistivity decreased gradually. A practical engineering application of this theory is also provided.

Sr2Mn0.5Hf1.5O6-δ double perovskite oxides: Structural, dielectric, magnetic, optical and transport properties

Double perovskite (DP) oxides with a chemical formula of A2B′B”O6 exhibit intriguing physical properties and structural flexibilities, which are widely used as a host structure to explore the novel candidates of half-metallic ferro-/ferrimagnetic materials. In this work, we have synthesized ferromagnetic Sr2Mn0.5Hf1.5O6-δ (SMHO) DP powders via solid-state reaction method. The powders had a magnetic Curie temperature up to 600 K, saturation magnetization of 0.59 emu/g at 2 K, and magnetic coercive field of 450 Oe. The SMHO ceramics displayed a butterfly-like magnetoresistance (MR)-H curve at 2 K due to the intergranular tunneling effect, and the MR (2 K, 7 T) value was −2.8 %. Structural investigations demonstrated the SMHO powders crystallized in an orthogonal crystal structure with Pnma symmetry. SEM images displayed a spherical morphology of the SMHO powders with particle size distribution of 100–200 nm. Quantitative EDS (energy dispersive X-ray spectra) data give out the percentage of Sr, Mn, Hf and O elements presented in approximately stoichiometric proportion. XPS spectra results confirmed the existence of Sr2+, Mn4+, and Hf4+/Hfx+(x＜4) ions in the powders, and oxygen elements were presented as the lattice oxygen and adsorbed oxygen species, respectively. Resistivity of the SMHO ceramics decreased continuously as the temperature increased from 2 K to 800 K, exhibiting a semiconductor behavior. The electrical transport data were well fitted by thermal activation model, small polaron hopping model, and Mott’s variable range hopping model, respectively in different temperature regions. Optical measurements gave out an indirect bandgap of 2.12 eV for the SMHO powders. Our present work demonstrates that the SMHO oxides are attractive in high temperature spintronic devices and solar cells owing to the integration of high TC, significant negative MR and optical bandgap located in the visible light window.

Deep trap assisting elastico-mechanoluminescence in diphase non-piezoelectrics induced by tunneling effect

The sustainable conversion of mechanical energy into light (elastico-mechanoluminescence, EML) opens up possibilities for energy-saving, which is of pivotal significance in addressing the energy crisis. The concepts of piezophotonics and the piezoelectric field's dependence on the probability of charge carriers detrapping have been thoroughly developed in explaining EML. Nevertheless, in contrast to the EML triggered by the piezoelectricity model, strong elastico-mechanoluminescence phenomena have also been frequently discovered in non-piezoelectric materials. Is the working principle different? This paper provides physical insight into the reconfigurable EML phenomena of intrinsic non-piezoelectric systems. It emphasizes the exploration of the mechanism through comprehensive analysis of trap information, de-trapping processes, and the lifetime of charge carriers in traps. We demonstrate the assistance of deep trap to enhance the red EML mode in a diphase centrosymmetric luminescent host through the electron tunneling effect. This advancement supports the progress of non-piezoelectric EML dielectrics and offers an appealing alternative approach in this field.

Near-field radiative heat transfer between nanoporous GaN films

Photon tunneling effects give rise to surface waves, amplifying radiative heat transfer in the near-field regime. Recent research has highlighted that the introduction of nanopores into materials creates additional pathways for heat transfer, leading to a substantial enhancement of near-field radiative heat transfer (NFRHT). Being a direct bandgap semiconductor, GaN has high thermal conductivity and stable resistance at high temperatures, and holds significant potential for applications in optoelectronic devices. Indeed, study of NFRHT between nanoporous GaN films is currently lacking, hence the physical mechanism for adding nanopores to GaN films remains to be discussed in the field of NFRHT. In this work, we delve into the NFRHT of GaN nanoporous films in terms of gap distance, GaN film thickness and the vacuum filling ratio. The results demonstrate a 27.2% increase in heat flux for a 10 nm gap when the nanoporous filling ratio is 0.5. Moreover, the spectral heat flux exhibits redshift with increase in the vacuum filling ratio. To be more precise, the peak of spectral heat flux moves from ω = 1.31 × 1014 rad⋅s−1 to ω = 1.23 × 1014 rad⋅s−1 when the vacuum filling ratio changes from f = 0.1 to f = 0.5; this can be attributed to the excitation of surface phonon polaritons. The introduction of graphene into these configurations can highly enhance the NFRHT, and the spectral heat flux exhibits a blueshift with increase in the vacuum filling ratio, which can be explained by the excitation of surface plasmon polaritons. These findings offer theoretical insights that can guide the extensive utilization of porous structures in thermal control, management and thermal modulation.

Investigation of Contact Surface Changes and Sensor Response of a Pressure-Sensitive Conductive Elastomer

The pressure-sensing mechanisms of conductive elastomers, such as conductive networks, and tunneling effects within them have been extensively studied. However, it has become apparent that external pressure can significantly impact the contact area of polymeric materials. In this study, we will employ a commercially available conductive elastomer to investigate changes in resistance and contact surface under external pressure. Resistance measurements will be taken with and without applying conductive grease to the surface of the elastomer. This allows us to observe changes in resistance values associated with pressure variations. Furthermore, as pressure is applied to the conductive elastomer, the contact area ratio increases. Such an increase in the contact area and its correlation to changes in conductance values will be assessed.

Evaluation of p-GaN HEMTs degradation under high temperatures forward and reverse gate bias stress

In this study, the degradation behavior and physical mechanism of the p-GaN HEMT devices under high-temperature gate bias (HTGB) with +5 V and −5 V were investigated. The DC characteristics show that the device after forward HTGB stress exhibits an obvious negative threshold voltage (Vth ) shift, while the device after reverse HTGB exhibits a negligible shift. The following explanations could be given for the deterioration mechanism: a portion of the two-dimensional hole gas (2DHG) accumulated in the p-GaN layer at the p-GaN/AlGaN interface under long-term forward bias may fill the trap in the AlGaN layer through the tunneling effect. In addition, the drain-source on-resistance of the device had increased after +5 V HTGB stress, and a distinct decrease of accumulated capacitance was observed in the Cg -Vg curve. It indicates a degradation of the gate quality of the device after applying a forward-biased HTGB stress.

Study of the influence of virtual guard ring width on the performance of SPAD detectors in 180 nm standard CMOS technology

The influence of the virtual guard ring width (GRW) on the performance of the p-well/deep n-well single-photon avalanche diode (SPAD) in a 180 nm standard CMOS process was investigated. TCAD simulation demonstrates that the electric field strength and current density in the guard ring are obviously enhanced when GRW is decreased to 1 μm. It is experimentally found that, compared with an SPAD with GRW = 2 μm, the dark count rate (DCR) and afterpulsing probability (AP) of the SPAD with GRW = 1 μm is significantly increased by 2.7 times and twofold, respectively, meanwhile, its photon detection probability (PDP) is saturated and hard to be promoted at over 2 V excess bias voltage. Although the fill factor (FF) can be enlarged by reducing GRW, the dark noise of devices is negatively affected due to the enhanced trap-assisted tunneling (TAT) effect in the 1 μm guard ring region. By comparison, the SPAD with GRW = 2 μm can achieve a better trade-off between the FF and noise performance. Our study provides a design guideline for guard rings to realize a low-noise SPAD for large-array applications.

Large-Eddy Simulations of the Tropical Cyclone Boundary Layer at Landfall in an Idealized Urban Environment

Abstract Populated urban areas along many coastal regions are vulnerable to landfalling tropical cyclones (TCs). To the detriment of surface parameterizations in mesoscale models, the complexities of turbulence at high TC wind speeds in urban canopies are presently poorly understood. Thus, this study explores the impacts of urban morphology on TC-strength winds and boundary layer turbulence in landfalling TCs. To better quantify how urban structures interact with TC winds, large-eddy simulations (LESs) are conducted with the Cloud Model 1 (CM1). This implementation of CM1 includes immersed boundary conditions (IBCs) to represent buildings and eddy recycling to maintain realistic turbulent flow perturbations. Within the IBCs, an idealized coastal city with varying scales is introduced. TC winds impinge perpendicularly to the urbanized coastline. Numerical experiments show that buildings generate distinct, intricate flow patterns that vary significantly as the city structure is varied. Urban IBCs produce much stronger turbulent kinetic energy than is produced by conventional surface parameterizations. Strong effective eddy viscosity due to resolved eddy mixing is displayed in the wake of buildings within the urban canopy, while deep and enhanced effective eddy viscosity is present downstream. Such effects are not seen in a comparison LES using a simple surface parameterization with high roughness values. Wind tunneling effects in streamwise canyons enhance pedestrian-level winds well beyond what is possible without buildings. In the arena of regional mesoscale modeling, this type of LES framework with IBCs can be used to improve parameters in surface and boundary layer schemes to more accurately represent the drag coefficient and the eddy viscosity in landfalling TC boundary layers. Significance Statement This is among the first large-eddy simulation model studies to examine the impacts of tropical cyclone–like winds around explicitly resolved buildings. This work is a step forward in bridging the gap between engineering studies that use computational fluid dynamics models or laboratory experiments for flow through cities and mesoscale model simulations of landfalling tropical cyclones that use surface parameterizations specialized for urban land use.