Energy Width Research Articles

Interference effects in coupled triple quantum dot systems

Electronic transport through a coupled triple quantum dot (TQD) system is theoretically studied using Equilibrium Green’s function approach. The TQD system is systematically investigated for T-shape configuration and triangular shape configuration. T-shape (triangular shape) configuration corresponds to the TQD structure in which two quantum dots (QD)s are connected to the left and right leads in series and third one is side coupled to the right one (both) the QDs. In the electronic transmission spectrum of T-shape configuration, it is found that an antiresonance peak occurs at the QDs energy level and width of the peak increases with the increase in the tunnel coupling of the side coupled QD. Further, an asymmetric Fano lineshape is also observed while investigating transition from the T-shape to the triangular shape configuration. Interestingly, this Fano peak is found to occur when side coupled QD is weakly coupled to both the serially coupled QDs and its appearance becomes more prominent when the side coupled QD is symmetrically coupled to both the QDs. Both these effects reveal quantum interference effects that take place between discrete states and the continuum in electron transport through multiple channels in T-shape and triangular shape geometries.

Magnetic Amplification at Yb3+ "Designer Defects" in the van der Waals Ferromagnet CrI3.

The two-dimensional (2D) van der Waals ferromagnet CrI3 has been doped with the magnetic optical impurity Yb3+ to yield materials that display sharp multiline Yb3+ photoluminescence (PL) controlled by the magnetism of CrI3. Magneto-PL shows that Yb3+ magnetization is pinned to the magnetization of CrI3. An effective internal field of ∼10 T at Yb3+ is estimated, attributed to strong in-plane Yb3+-Cr3+ superexchange coupling. The anomalously low energy of Yb3+ PL in CrI3 reflects relatively high Yb3+-I- covalency, contributing to Yb3+-Cr3+ superexchange coupling. The Yb3+ PL energy and line width both reveal the effects of spontaneous zero-field CrI3 magnetic ordering within 2D layers below TC, despite the absence of net magnetization in multilayer samples. These results illustrate the use of optical impurities as "designer defects" to introduce unique functionality to 2D magnets.

Effect of intracavity loss on output stability and reliability of solid-state mode-locked lasers with SESAM

Mode-locked lasers have been widely used, but high-quality stable operation is still the key factor affecting their reliability. We present a numerical simulation of the dynamics of a passively mode-locked laser using saturable absorbers, and the effects of gain and loss on output stability are discussed. The results reveal that, in the case of a sudden and intense disturbance, the laser loses its lock, and the mode-locking state can be restored by stabilizing the cavity loss, whereas the mode-locking state of the laser is more robust to the slowly changing cavity loss. The laser output energy, spectrum, and pulse width vary with the cavity loss. If slow-varying cavity losses occur during mode-locked laser operation, the laser energy, pulse width, and spectrum must be monitored in real time when there is a high requirement for energy stability, pulse width, and spectral stability.

On the Peculiarities of Studying Unbound Excited States of 4He Nucleus by α + 3H Interaction

Due to the alpha-particle beam interaction with tritium, the two-dimensional spectra of tt, t3He, and dd coincidences are obtained using the particle-decay spectroscopy from three-particle 3H(α,tt)p, 3H(α,t 3He)n, and 3H(α,td)d reactions (Eα = 67.2 MeV). Excitation energies and energy widths for seven excited 4He states, as well as the ratio of their different decay modes, namely t + p, n + 3He, and d + d, are obtained by using the Monte Carlo method.

The Initial Test of a Micro-Joules Trigger, Picosecond Response, Vertical GaN PCSS

To meet the miniaturization of all-solid-state high-power microwave drive technology based on photoconductive semiconductor switches (PCSSs), a vertical gallium nitride (GaN) PCSS that is triggered by a micro-joules energy and picoseconds pulse width laser is presented. The device has showed low triggering optical energy and fast response. When the bias-voltage is 3 kV and optical energy is 33 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{J}$ </tex-math></inline-formula> , the photocurrent, on-state resistance, rise-fall time and quantum efficiency of the PCSS are 4.28 A, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$650.5~\Omega $ </tex-math></inline-formula> , 412/370 ps and 0.28%, respectively. It is anticipated that GaN-based PCSS will have a practical application in future radio frequency (RF) microwave systems for military purposes.

Tunable spectral narrowing enabling the functionality of graphene qubit circuits at room temperature

Electrically controllable quantum coherence in quantum dot clusters and arrays based on graphene stripes with zigzag atomic edges (ZZ-stripes) is studied using the Dirac equation and S-matrix technique. We find that respective multiqubit circuits promise stable operation up to room temperatures when the coherence time is prolonged up by a few orders of magnitude through the intrinsic spectral narrowing owing to electron transport between at bands in adjacent sections. Respectively, the coupling of qubits to a noisy environment is diminished, while the inelastic electron-phonon scattering is suppressed. The Stark splitting technique enables a broad range of operations such as all{electrical tuning of the energy level positions and width, level splitting, controlling of the inter-qubit coupling, and the coherence time. At the resonant energies, the phase coherence spreads over thousands of periods. Such phenomena potentially can be utilized in quantum computing and communication applications at room temperature.

Surface atomic structures of nickel plating films reacted with methane at high temperature

The surface structure of Ni plating films that were reacted with methane at 800°C was investigated using scanning electron microscopy and transmission electron microscopy (TEM). The surface of the Ni plating film was eroded by the reaction with methane, resulting in a nano‐roughened surface with a hexagonal close‐packed structure with a thickness of ~ 3 nm. The carbon layer deposited on the Ni plating film was evaluated by electron energy loss spectroscopy. An increase in the π + σ bonding energy and full width at half maximum of the π* peak was observed on moving toward the Ni plating film surface, indicating an increase in the hydrogenated or oxidized carbon atoms on the surface of the Ni plating film.

Annular energy and radial dose distributions study for a wide range of ions of different equal LET groups in water

Annular energy distribution, AED is a new concept deduced from radial dose, RDD that enables one to draw a map of energy-dose distribution around the ion's path at the nanometer scale better than the ordinary radial dose. The distribution of energy for different equal LET groups of ions of the same LET (keV/μm) were studied using this concept. Annular energy distributions, AEDs for 185 ions impeded in water medium were studied using Katz radial dose formula. AED was calculated using Butts-Katz and Tabata electron range-energy (R-E) relations and were compared. AED and shell annular energy distribution, SAED for those ions were mapping and confirming that energy distributions for ions of the same LET are not the same. AED growth with annular width r=0.1(nm)⟶Rmin(nm) showing a peak at the maximum annular energy width, rMAEW. Butts-Katz and Tabata show same annular energy distribution peaks of the same value, however, Tabata shows that energy is distributed over a wide range than Butts-Katz. Thus, Butts-Katz R-E relation is recommended and considered. AED for the studied 185 ions shows a peak at certain width called the maximum annular energy width, rMAEW. This rMAEW showed a monotonic increasing function with ion's β2. The total annular energy distribution, TAED for the different ions were determined and it shows a linear increasing function of the ion's (Z*/β)2.

Evaluation of Pulsed Electric Fields (PEF) Parameters in the Inactivation of Anisakis Larvae in Saline Solution and Hake Meat.

Larvae of the nematode family Anisakidae are capable of causing parasitic infections in humans associated with the consumption of fishery products, leading to intestinal syndromes and allergic reactions. Anisakidae larvae are widely distributed geographically, with rates of parasitism close to 100% in certain fish species. Methods need to be established for their inactivation and elimination, especially in fishery products that are to be consumed raw, pickled, or salted, or which have been insufficiently treated to kill the parasite. Many strategies are currently available (such as freezing and heat treatment), but further ones, such as pulsed electric fields (PEF), have hardly been investigated until now. This study focuses on the experimental evaluation of the efficacy of PEF in the inactivation of Anisakis spp. larvae in terms of electric field strength, specific energy, and pulse width, as well as on the evaluation of the quality of fish samples after PEF treatment. Results show that viability of Anisakis was highly dependent on field strength and specific energy. Pulse width exerted a considerable influence at the lowest field strengths tested (1 kV/cm). Central composite design helped to define a PEF treatment of 3 kV/cm and 50 kJ/kg as the one capable of inactivating almost 100% of Anisakis present in pieces of hake, while affecting the investigated quality parameters (moisture, water holding capacity, and cooking loss) to a lesser extent than freezing and thawing. These results show that PEF could serve as an alternative to traditional freezing processes for the inactivation of Anisakis in fish.

Can room-temperature data for tunneling molecular junctions be analyzed within a theoretical framework assuming zero temperature?

Routinely, experiments on tunneling molecular junctions report values of conductances (GRT) and currents (IRT) measured at room temperature. On the other hand, theoretical approaches based on simplified models provide analytic formulas for the conductance (G0K) and current (I0K) valid at zero temperature. Therefore, interrogating the applicability of the theoretical results deduced in the zero-temperature limit to real experimental situations at room temperature (i.e., GRT ≈ G0K and IRT ≈ I0K) is a relevant aspect. Quantifying the pertaining temperature impact on the transport properties computed within the ubiquitous single-level model with Lorentzian transmission is the specific aim of the present work. Comprehensive results are presented for broad ranges of the relevant parameters (level's energy offset ε0 and width Γa, and applied bias V) that safely cover values characterizing currently fabricated junctions. They demonstrate that the strongest thermal effects occur at biases below resonance (2|ε0| - δε0 - 0.3 ≲ |eV| - 0.3 ≲ 2|ε0|). At fixed V, they affect an ε0-range whose largest width δε0 is about nine times larger than the thermal energy (δε0 ≈ 3πkBT) at Γa → 0. The numerous figures included aim to convey a quick overview on the applicability of the zero-temperature limit to a specific real junction. In quantitative terms, the conditions of applicability are expressed as mathematical inequalities involving elementary functions. They constitute the basis of a proposed interactive data-fitting procedure, which aims to guide experimentalists interested in data processing in a specific case.

К аналитической теории магнитных скирмионов высокого порядка в неоднородном магнитном поле

It is shown that axially symmetric inhomogeneous magnetic fields can lead to stabilization of higher-order magnetic skyrmions with topological charge |Q| &gt; 1 due to orbital effects. We describe the analytical theory on the energy, size, and domain wall width of the such skyrmions in a power-law inhomogeneous fields, with a parameters corresponding to strongly correlated electron systems. The results obtained may have applications in describing the formation of nontrivial magnetic structures in inhomogeneous fields of superconducting vortices in heterostructures superconductor - chiral magnet of the type [Ir1Fe0.5Co0.5Pt1]10 /MgO/Nb.

To an analytical theory of higher-order magnetic skyrmions in nonuniform magnetic fields

It is shown that axially symmetric inhomogeneous magnetic fields can lead to stabilization of higher-order magnetic skyrmions with topological charge |Q|&amp;gt;1 due to orbital effects. We developed the analytical theory on the energy, size, and domain wall width of the such skyrmions in a power-law inhomogeneous fields, with a parameters corresponding to strongly correlated electron systems. The results obtained may have applications in describing the formation of nontrivial magnetic structures in inhomogeneous fields of superconducting vortices in heterostructures superconductor --- chiral magnet of the type [Ir1Fe0.5Co0.5Pt1]10/MgO/Nb. Keywords: magnetic skyrmions, nonuniform magnetic fields.

Understanding and controlling the depth sensitivity of scanning probe based infrared imaging and nanospectroscopy for buried polymeric structures.

Atomic force microscopy paired with infrared spectroscopy (AFM-IR) is a robust technique for investigating complex polymer blends and composites' nanoscale surface topography and chemical composition. In this work, we measured bilayer polymer films to study the effect of laser power, laser pulse frequency, and laser pulse width on the depth sensitivity of the technique. Unique bilayer polystyrene (PS) and polylactic acid (PLA) samples with various film thicknesses and blend ratios were prepared. The depth sensitivity characterized by the amplitude ratio of the resonance bands of PLA and PS was monitored as the thickness of the top barrier layer was incrementally increased from tens of nanometers to hundreds of nanometers. In addition, incrementally increasing the incident laser power resulted in greater depth sensitivity due to the enhanced thermal oscillations generated in the buried layer. In contrast, incrementally increasing the laser frequency increased the surface sensitivity, as indicated by a reduced PLA/PS AFM-IR signal ratio. Finally, the dependence of the depth sensitivity on the laser pulse width was observed. Consequently, by precisely controlling the laser energy, pulse frequency, and pulse width, one can finely control the depth sensitivity of the AFM-IR tool from 10 nm to 100 nm. Our work provides the unique capability to study buried polymeric structures without the need for tomography or destructive etching.

First application of a microscopic K−NN absorption model in calculations of kaonic atoms

Strong interaction energy shifts and widths in kaonic atoms are calculated for the first time using microscopic $K^- N$ + $K^- NN$ potentials derived from $K^- N$ scattering amplitudes constructed within SU(3) chiral coupled-channels models of meson-baryon interactions. The in-medium modifications of the free-space amplitudes due to the Pauli correlations are taken into account. The $K^-N+K^-NN$ potentials evaluated for 23 nuclear species are confronted with kaonic atoms data. The description of the data significantly improves when the $K^-NN$ absorption is included. To get $\chi^2$ as low as for the $K^-N+$phenomenological multi-nucleon potential an additional phenomenological term, accounting for $K^{-}-3N(4N)$ processes, is still needed. However, density dependence of this phenomenological term points out some deficiencies in the microscopic potentials and further improvements of the applied model are thus desirable. The calculated branching ratios for $K^-N$ and $K^-NN$ absorption channels in the $^{12}$C$+K^-$ atom are in reasonable agreement with the old bubble chamber data, as well as with the latest data from the AMADEUS Collaboration.

Near-Monochromatic Tuneable Cryogenic Niobium Electron Field Emitter.

Creating, manipulating, and detecting coherent electrons is at the heart of future quantum microscopy and spectroscopy technologies. Leveraging and specifically altering the quantum features of an electron beam source at low temperatures can enhance its emission properties. Here, we describe electron field emission from a monocrystalline, superconducting niobium nanotip at a temperature of 5.9K. The emitted electron energy spectrum reveals an ultranarrow distribution down to 16meV due to tunable resonant tunneling field emission via localized band states at a nanoprotrusion's apex and a cutoff at the sharp low-temperature Fermi edge. This is an order of magnitude lower than for conventional field emission electron sources. The self-focusing geometry of the tip leads to emission in an angle of 3.7°, a reduced brightness of 3.8×10^{8} A/(m^{2} sr V), and a stability of hours at 4.1nA beam current and 69meV energy width. This source will decrease the impact of lens aberration and enable new modes in low-energy electron microscopy, electron energy loss spectroscopy, and high-resolution vibrational spectroscopy.

Determination of band tail widths in MOCVD grown InGaN single layer within GaN based p-i-n LED structure through photo-induced measurements

Within a p-i-n LED structure, energy band gaps of MOCVD grown %10 In content InGaN and GaN layers were obtained through traditional UV–Visible transmission-absorption measurements and utilizing surface photovoltage (SPV) and spectral photoconductivity (SPC) measurements. Moreover, all applied techniques determined that the total band offset between InGaN and GaN layers were around 0.3–0.4 eV. Furthermore, the temperature dependence of band gaps of each InGaN and GaN layer was analyzed through a modified Varshni relation where both Varshni coefficients and band tail energy width were explored. Band tails in a modified Varshni relation, SPV and SPC measurements were in agreement with each other and originated Franz-Keldysh Effect attributed to the presence of photon assisted tunneling.

High relative permittivity and excellent dye photo-elimination: Pure and (Zr4+, Y3+, Sb5+) multi-doped anatase TiO2 structure

Herein, multifunctional characteristics including solar photocatalytic, dielectric constant and ac electrical conductivity have been studied for pure and Zr4+, Y3+ and Sb5+ multidoped TiO2 n-type semiconductor. Pure, Zr doped, (Zr, Y) codoped and (Zr, Y, Sb) tridoped TiO2 with chemical compositions of TiO2, Ti0.98Zr0.02O2, Ti0.96Zr0.02Y0.02O2 and Ti0.94Zr0.02Y0.02Sb0.02O2 were prepared via a low cost coprecipitation technique. All compositions reveal a pure single phase of anatase TiO2 structure with different unit cell volume due to the differences in ionic radii between parent cation (Ti4+ = 0.605 Å) and dopants ions (Zr4+ = 0.72 Å), (Y3+ = 0.9 Å) and (Sb5+ = 0.6 Å). Morphological changes for TiO2 particles were seen due to incorporation of Zr4+, Y3+ or Sb5+ cations into TiO2 lattice. Optically, Zr4+, Y3+ and Sb5+ ions cause a red shift for the absorption edge and reduce the width of the bang gap energy of TiO2 as well as enhance its refractive index value. High dielectric constant of 2214 (42 Hz) was detected for Ti0.94Zr0.02Y0.02Sb0.02O2 composition. Ti0.94Zr0.02Y0.02Sb0.02O2 sample reveals the highest ac electrical conductivity (σac) values compared to undoped TiO2, Ti0.98Zr0.02O2 and Ti0.96Zr0.02Y0.02O2 samples. High efficiency (∼100%) and fast (20–40 min) solar photodegradation characteristics for 10 ppm Congo red (CR) was realized via TiO2 and Ti0.96Zr0.02Y0.02O2 catalysts. For 40 ppm CR, pure TiO2 exhibits a high photocatalytic activity of 80% after 120 min of sunlight irradiation. Interestingly, this study also illustrates that the starting materials (titanium butoxide-butanol solvent) used in the synthesis process play a significant role in the phase structure as well as the ultimate photocatalytic properties of TiO2 based compositions.

Statistical Analysis of Machining Parameters on Burr Formation, Surface Roughness and Energy Consumption during Milling of Aluminium Alloy Al 6061-T6.

Due to the increasing demand for higher production rates in the manufacturing sector, there is a need to manufacture finished or near-finished parts. Burrs and surface roughness are the two most important indicators of the surface quality of any machined parts. In addition to this, there is a constant need to reduce energy consumption during the machining operation in order to reduce the carbon footprint. Milling is one of the most extensively used cutting processes in the manufacturing industry. This research was conducted to investigate the effect of machining parameters on surface roughness, burr width, and specific energy consumption. In the present research, the machining parameters were varied using the Taguchi L9 array design of experiments, and their influence on the response parameters, including specific cutting energy, surface finish, and burr width, was ascertained. The response trends of burr width, energy consumption, and surface roughness with respect to the input parameters were analyzed using the main effect plots. Analysis of variance indicated that the cutting speed has contribution ratios of 55% and 47.98% of the specific cutting energy and burr width on the down-milling side, respectively. On the other hand, the number of inserts was found to be the influential member, with contribution ratios of 68.74% and 35% of the surface roughness and burr width on the up-milling side. The validation of the current design of the experiments was carried out using confirmatory tests in the best and worst conditions of the output parameters.

Chemical Bonding Effects and Physical Properties of Noncentrosymmetric Hexagonal Fluorocarbonates ABCO3F (A: K, Rb, Cs; B: Mg, Ca, Sr, Zn, Cd).

The present work applied the methods of density functional theory and the van der Waals interaction PBE + D3(BJ) on the basis of localized orbitals of the CRYSTAL17 package. It featured the effect of interactions between structural elements of fluorocarbonates ABCO3F (A: K, Rb, Cs; B: Mg, Ca, Sr, Zn, Cd) on their elastic and vibrational properties. The hexagonal structures proved to consist of alternating ···B-CO3··· and ···A-F··· layers in planes ab, interconnected along axis c by infinite chains ···F-B-F···, where cations formed polyhedra AOnF3 and BOmF2. The calculations included the band energy structure, the total and partial density of electron states, the energy and band widths of the upper ns- and np-states of alkali and alkaline-earth metals, as well as nd-zinc and nd-cadmium. For hydrostatic compression, we calculated the parameters of the Birch–Murnaghan equation of state and the linear compressibility moduli along the crystal axes and bond lines. We also defined the elastic constants of single crystals to obtain the Voigt–Reuss–Hill approximations for the elastic moduli of polycrystalline materials. The study also revealed the relationship between the elastic properties and the nature of the chemical bond. Hybrid functional B3LYP made it possible to calculate the modes of normal long-wavelength oscillations, which provided the spectra of infrared absorption and Raman scattering. Intramolecular modes ν1 and ν4 with one or two maxima were found to be intense, and their relative positions depended on the lengths of nonequivalent C–O bonds.

Characterization of fracture toughness and damage zone of double network hydrogels

Double-network (DN) hydrogels have received extensive attention owing to their excellent mechanical properties such as high fracture toughness. It is widely accepted that the toughening mechanism of DN gels is based on the mutual interaction of two contrasting interpenetrating networks. However, the quantitative interpretation of this toughening mechanism during fracture is still lacking; there are also some contradictions regarding the fracture toughness. In this study, we developed a quantitative framework to decompose the fracture toughness and feature size of the crack-tip field. Through extensive tearing tests with varying free widths of the tearing specimens, we propose an exponential function to describe the relationship between the apparent fracture energy and free width. Using the proposed function, the fracture energy and feature size of the dissipation zone were decomposed into their different components, and their quantitative values were obtained. Tearing tests were also conducted on prestretched DN gels, which showed that the intrinsic fracture energy is related to the historical deformation. Finally, we established an intrinsic fracture model with a clear physical meaning by considering the complex interactions between the two interpenetrating networks of DN gels. The model revealed the physical mechanism behind the dependence of the intrinsic fracture energy of DN gels on the historical loading. The contributions of the two interpenetrating networks of DN gels to the intrinsic fracture energy were quantitatively decomposed by the model, and the feature size of the intrinsic field was also obtained. The study reveals the physical inconsistencies in some opinions about DN gel fracture and resolves some paradoxes on the toughness of DN gels.