Effect Of External Field Research Articles

Effect of external fields in high Chern number quantum anomalous Hall insulators

A quantum anomalous Hall state with a high Chern number has so far been realized in multilayer structures consisting of alternating magnetic and undoped topological insulator (TI) layers. However, in previous proposals, the Chern number can only be tuned by varying the doping concentration or the width of the magnetic TI layers. This drawback largely restricts the applications of dissipationless chiral edge currents in electronics since the number of conducting channels remains fixed. In this paper, we propose a way of varying the Chern number at will in these multilayered structures by means of an external electric field applied along the stacking direction. In the presence of an electric field in the stacking direction, the inverted bands of the unbiased structure coalesce and hybridize, generating new inverted bands and collapsing the previously inverted ones. In this way, the number of Chern states can be tuned externally in the sample, without the need for modifying the number and width of the layers or the doping level. We showed that this effect can be uncovered by the variation of the transverse conductance as a function of the electric field at constant injection energy at the Fermi level.

The Absorption Properties of One‐Dimensional Spherical Photonic Crystals Based on Magnetized Ferrite Materials

AbstractBased on a spherical coordinate system and Maxwell's set of equations, the calculation formulas of one‐dimensional (1‐D) magnetized ferrite spherical photonic crystals (MFSPCs) are obtained and treated with the solution method of the spherical Bessel equations. Combined with the conventional transmission matrix method, expressions for the absorptance, reflectance, and transmittance of the 1‐D MFSPCs are given. 1‐D MFSPCs consisting of the general dielectric and Yttrium iron garnet (YIG) are also designed to verify the correctness of the conclusions. Variables such as external magnetic field, incidence angle, initial radius, and YIG thickness effects on the features of such 1‐D MFSPCs are also discussed. The transformation of the external magnetic field has a linear relationship with the position of the absorption band (AB). The three variables of incidence angle, initial radius, and YIG thickness have a substantial influence on the width and position of the AB, which can be adjusted according to the actual demand and are of high application significance. The results of this study can be helpful for the design of multifunctional absorbers and radome.

Transforming Navier‐stokes equation to a fourth order nonlinear differential equation for the study of electrolyte flow in a circular microchannel

AbstractIn this paper, analytical solutions are derived for the study of steady‐state electrolyte flow in a circular microchannel under the simultaneous effects of an external electric field and uniform wall injection. The Navier‐Stokes equations containing an axial linear electric body force are transformed to a fourth‐order nonlinear differential equation and solved analytically using a series solution method. The most important results are presented and discussed in terms of radial Reynolds number and a fundamental non‐dimensional electric field parameter. The Electrical Double Layer theory is employed to model the effects of external electric field. Analytical relations are given for velocity profiles, exit flow rate, and total pressure drop in the microchannel. The results show that a high‐intensity electric field can completely reverse the velocity profile or make it more flat in the presence of wall injection. This electric effect can be used in practical applications to control the shear stress, heat, or mass transfer in microchannels or microelectromechanical systems. In addition, various graphs are presented showing simultaneous effects of electric field and wall injection of the same fluid on the flow physics.

Ferroelectric water chains in carbon nanotubes: Creation and manipulation of ordered quantum phases.

Systems composed of molecular rotors are promising candidates as quantum devices. In this work, we employ our recently developed density matrix renormalization group approach to study such a rotor system, namely, linear chains of rotating para-water molecules encapsulated in a (6,5)-carbon nanotube. We show that the anisotropic environment provided by the nanotube breaks the inversion symmetry of the chain. This symmetry breaking lifts the degeneracy of the ground state and leads to a splitting between the left- and right-polarized states. In turn, a ferroelectric phase in nanoscopic systems is created, with a polarization that can be switched in a manner analogous to that of a supramolecular qubit. We present results for a few low-lying states and discuss the effect of external electric fields on the energy splitting and the occurrence of a quantum phase transition.

Study of the Effect of External Magnetic Fields on the Parameters of the Electrical Communications Probing System for a Microtunneling Shield

The issues were reviewed in assessing external electromagnetic fields’ effect on the parameters of an electrical power line probing system based on three-component ferroprobes for detecting active underground power cable lines during microtunnel construction using the thrust boring method (by tunneling shield) in densely populated urban areas. A study was conducted on the change in the topology of the energized cable magnetic field located in the external magnetic field area created by operating electrical equipment under the influence of an external electromagnetic field and a tunneling shield with installed magneto-sensitive detectors. Experimental studies of the probing system were made. Options have been proposed for compensating the inductance component of the external magnetic field during tunnel driving in urban development and industrial area conditions.

Analysis of Magneto-Thermo-Bioconvection of Nanofluid Containing Gyrotactic Microorganisms Through Porous Media

The present work aims to study the combined effect of external magnetic field and heating from below on the bioconvection of nanofluid containing gyrotactic microorganisms. Modified Maxwell’s equations and generalized Buongiorno’s model are used to frame the flow constitutive equations of nanofluid saturated in the Darcy-Brinkman porous medium. The present investigation has been done in the framework of linear stability. The resulting eigenvalue problem along with boundary conditions has been solved using Chebyshev-Gauss-Lobato Spectral Method. Appropriate transformations are used to convert Neumann boundary conditions into Dirichlet’s one. The influence of various pertinent parameters on the critical thermal Rayleigh number has been shown through graphs and tables. It has been observed that magnetic field stablizes the system whereas fast moving microorganisms hasten the onset of convection.

Effects of Electric Field and External Magnetic Field on the Electronic and Thermoelectric Properties of the h-BAs Monolayer and Bilayer: Tight-Binding Approach

Newly, two-dimensional (2D) materials atoms of groups IV and III-V have obtained extensive attention due to their novel properties. In this work, we apply the tight-binding model and Green’s function approach to the hexagonal boron arsenide (h-BAs) monolayer and bilayer to investigate their electronic and thermoelectric properties. We find that the h-BAs monolayer behaves as a p-type semiconductor and it can be changed to the n-type by applying the external magnetic field. Also, the h-BAs bilayer with (A-A) stacked has a semi-metallic property but (A-B) stacked is a semiconductor. The results show that the band gap can be controlled by applying an electric field and an external magnetic field. We obtain that the thermal and electrical conductivity of the h-BAs monolayer and bilayer increase in the presence of an electric field and an external magnetic field. More, controlling the Seebeck coefficient of the material is a unique phenomenon that provides advanced applications for these materials in thermoelectric coolers and waste heat harvesting. Here, we have been able to regulate the Seebeck coefficient of the h-BAs monolayer and bilayer by using the electric and external magnetic fields.

The effect of external magnetic field on osteogenic and antimicrobial behaviour of surface-functionalized custom titanium chamber with iron nanoparticles. A preliminary research.

The controlled responsive characteristics of iron nanoparticles (FeNp) in magnetic fields make them an attractive prospect in this field. In the presence of a magnetic field, FeNp can significantly impact cell behaviour, leading to breakthroughs in nanotechnology. The aim is to determine the possible applications of iron nano particles (FeNp), and induced magnetic exposure role in osteoconduction and antibacterial activity. The custom-grade IV titanium (Ti)hollow chamber is fabricated, surface treated with FeNp. Each titanium chamber contained neodymium, iron, and boron magnet disc, and the effect of FeNp on osteoblast-like cells (MG63) was evaluated in terms of cell attachment and survivability, morphological characteristics, particle absorption, and antibacterial properties. The effects of cellular uptake of FeNp and their responses to subcellular thrust were studied using fluorescent microscopy. MTT was used to determine cell viability, and von Kossa histochemical staining was used to determine matrix mineralization. In the magnetized Ti chambers group, osteogenic activity and mineralization were considerably greater than in the control groups (p 0.05). With a p value of 0.027, the S. aureus and E. coli were resistant to the antibacterial properties of the FeNp modified titanium custom Ti chamber (MIC: 0.03135mg/mL and 0.02915mg/mL, respectively). The one-of-a-kind, in vitro, conveniently modelled, limited sample study sheds light on the effect of surface-functionalized titanium custom Ti chamber with FeNp on MG63. The use of magnetized FeNp-surfaced implants for long-term strategic bone tissue engineering and bacteriostatic implants.

Microscopic model of spin flip-flop processes in crystals doped by rare-earth ions

Flip-flop processes due to magnetic dipole-dipole interaction between neighboring ions in crystals doped by rare-earth ions are one of the mechanisms of relaxation between hyperfine levels. Modeling of this mechanism has so far been macroscopic, characterized by an average rate describing the relaxation of all ions. Here, however, we present a microscopic model of flip-flop interactions between individual nuclear spins of dopant ions. Every ion is situated in a unique local environment in the crystal, where each ion has different distances and a unique orientation relative to its nearest neighbors, as determined by the lattice structure. Thus each ion has a unique flip-flop rate and the collective relaxation dynamics of all ions in a bulk crystal is a sum of many exponential decays, giving rise to a distribution of rates rather than a single average decay rate. We employ this model to calculate flip-flop rates in ${\mathrm{Pr}}^{3+}$:${\mathrm{Y}}_{2}{\mathrm{SiO}}_{5}$ and show experimental measurements of population decay of the ground state hyperfine levels at $\ensuremath{\sim}2$ K. We also present a method to measure rates of individual transitions from hole burning spectra that requires significantly fewer fitting parameters in theoretical rate equations compared to earlier work. Furthermore, we measure the effect of external magnetic field on the flip-flop rates and observe that the rates slow down by two orders of magnitude in a field of 5--10 mT.

Combined effect of induced magnetic field and thermal radiation on ternary hybrid nanofluid flow through an inclined catheterized artery with multiple stenosis

The present article introduces a theoretical study of ternary hybrid nanoparticle (Cu–Ag–Au) on a two-dimensional blood flow through an inclined catheterized artery with multiple stenoses in the presence of wall slip. The combined effect of Non-linear thermal radiation and external induced magnetic field gives rise to innovative results in the current study. Further, the purpose of this study is to graphically observe the flow characteristics of tri-hybrid (Cu–Ag–Au), hybrid (Cu–Au), and single (Au) nanofluid flow through arteries with composite stenosis. This model involves tri-hybrid nanoparticles as part of the heat transfer process, as well as thermal radiation to further enhance the temperature rate. In the mathematical model, continuity, linear momentum, thermal energy, and Maxwell’s equations are simplified under the assumption of mild stenosis. The homotopy perturbation method is used for finding the analytical solution of non-linear PDE. With the help of contours, the flow pattern is also presented. This study indicates that magnetic force significantly controls the flow velocity and the expansion of the magnetic field, whereas the increase of radiation parameter does the opposite. Moreover, magnetic force and radiative heat reduces the pressure gradient and temperature in the blood flow, respectively, as well as thermal slip enhances the temperature distribution. These graphical outcomes instigate that the tri-hybrid nanoparticles are more helpful in attenuating the hemodynamics factors (such as blood velocity and temperature) as compared to the hybrid and single nanoparticles.

Effects of external fields on the nonlinear optical rectification and second harmonic generation of GaAs/GaAlAs zigzag quantum well

For the first time, the impact of externally applied static electric and magnetic field on the nonlinear optical rectification (NOR) and second harmonic generation (SHG) coefficients of GaAs/GaAlAs zigzag quantum well is theoretically investigated in this study. Additionally, we examined the effect of physical parameters such as width and depth of the structure on these coefficients. We have numerically solved the time-independent Schrödinger equation by using the diagonalization method under the effective mass approximation for obtaining subband energy levels and wave functions of the structure, and then we have used the compact density matrix method to obtain the analytical expressions of NOR and SHG coefficients. The obtained numerical results showed that when the magnitude of the externally applied electric and magnetic fields is increased, the peak position of NOR and SHG shifts to blue, and by increasing the width and potential depth of the quantum well, it shifts to red.

Chemical functionalization of SnAs monolayer: a first-principles study of SnAsX (X = Cl, Br, and I) monolayers

Chemical functionalization is one of the effective methods to tune the electronic properties of two-dimensional (2D) nanostructures. In this paper, we study the structural, electronic properties, and carrier mobilities of 2D SnAs monolayer functionalized by chlorine, bromine, and iodine, namely SnAsX (X = Cl, Br, and I), by means of density functional theory. The obtained results show that the 2D SnAsX are energetically, dynamically, and mechanically stable. While the 2D pristine SnAs monolayer exhibits metallic characteristics, SnAsX monolayers are direct semiconductors with direct band gaps. The influence of spin–orbit coupling on the electronic characteristics of SnAsX is significant, especially in the case of SnAsI monolayer. The direct–indirect gap transitions are found in all three SnAsX monolayers when the biaxial strain is applied. Meanwhile, the effects of external electric fields on the electronic characteristics of SnAsX are insignificant. Our calculated results indicate that SnAsX monolayers have very high electron mobility and their transport characteristics are directionally isotropic along the investigated transport directions.

The Effect of External Electric Field on the Conformational Integrity of Trypsin Inhibitor: A Molecular Model Study

The Effect of External Electric Field on the Conformational Integrity of Trypsin Inhibitor: A Molecular Model Study

Effect of oxygen configurations on the mechanical properties of graphene oxide

Understanding the mechanical properties of graphene oxide (GO) is the primary challenge for applications in materials engineering. The degree of oxidation and concentration of epoxide functional groups have been the main focus of previous mechanochemical studies. This work uses the reactive molecular dynamic simulations to reveal that the mechanical behavior of GO is strongly dependent on the epoxide configuration as well as its distribution. In this study, three main epoxide configurations—including top, bridge, and reside groups—decorate monolayer GO sheets with linear and random distributions. The distortion associated with epoxide groups creates diamond-like structures controlling the mechanical properties. Moreover, the orientation of those epoxide functional groups with applied loads has a dramatic impact on the mechanical response of GO. The effect of external electric fields on the mechanical properties of GO is another objective of this study. Findings exhibit that the electric field enhances the tensile toughness. This study demonstrates new aspects of GO as a functional material with potentials to control the mechanical properties through chemical compositions as well as external electric fields.

The solvent-driven impurity migration over graphene in the presence of electric field

The spontaneous migration and interconversion of oxygen functional groups over graphene sheet have promising high-tech applications. There is a remarkable activation energy barrier against epoxy movement over the graphene. To overcome this energy barrier, different methods have been proposed. In this paper, using first principles calculations, we study the effects of external electric fields and solvents on the activation energy barrier. Our findings show that: (i) epoxy migration on one side of the surface of a graphene sheet is facilitated when a hydroxyl group is adsorbed on the other side of the surface, (ii) applying a perpendicular electric field along the opposite direction of the adsorbed epoxy, weakens the corresponding C–O bonds strength and consequently decreases the activation energy barrier, (iii) the solvents with a larger dielectric constant cause decreasing the activation energy barrier, (iv) under applying an electric field for any given solution, the oxidized graphene is polarized and its solubility increases with decreasing activation energy barrier, and (v) the presence of a single vacancy in the graphene sheet, decreases the barrier. Our work reveals different physical aspects of the solubility of the oxidized graphene in the presence of electric field and vacancy defect on the surface of the graphene sheet.

Effect of external fields on pattern formation of charged grains in plasma

AbstractTwo‐dimensional cluster and pattern formation by charged grains in plasma under external harmonic force and transverse magnetic field is investigated using molecular dynamics simulation. It is found that, as a result of the Yukawa‐like grain‐grain interaction and the external fields, the asymptotic quasistationary state of an initially homogeneous and Maxwellian velocity distributed grain system can be a disk cluster with the grain trajectories having flowery zonal patterns.

Tuning of photovoltaic response in multiferroic heterojunction photodiodes by a built-in electric field and carrier transport: Effect of magnetization and ferroelectric polarization

Photovoltaic devices consisting of multiferroic thin films have been studied extensively for carrier separation regulated by a built-in electric field and the above bandgap. Here, a novel photodiode with photoelectric conversion efficiency (PCE) of 3.70% by introducing TiO2 and NiOx:5%Cu as the electron and the hole transport layers (ETL/HTL) on both sides of multiferroic bismuth layered perovskite oxide Bi2FeCrO6/Bi6Fe1.6Co0.2Ni0.2Ti3O18 (BFCO/BFCNT) heterojunction with the appropriate band gap were reported based on our recent studies. The results showed that BFCNT displays an Aurivillius structure, but BFCO is of a double perovskite, the bandgaps are ∼1.62 eV and 1.74 eV, respectively. The open-circuit voltage, short-circuit current density, and fill factor of the devices are 0.73 V, 10.5 mA·cm-2, and 48.3% separately under the illumination of 100 mW·cm-2 simulated AM 1.5 G solar light. Investigations of the effects of both external electric and magnetic fields on the photovoltaic responses delivered that the magnetization and ferroelectric polarization can effectively tune the built-in electric field and the carrier transport in multiferroics, thus offering an experimental and theoretical basis for further improving the performance of multiferroic photovoltaic devices.

Quantum memory-assisted entropic uncertainty and entanglement dynamics: two qubits coupled with local fields and Ornstein Uhlenbeck noise

Entropic uncertainty and entanglement are two distinct aspects of quantum mechanical procedures. The estimation of the entropic uncertainty is required for the increased accuracy and, hence, for the enhanced efficacy of quantum information processing tasks. In this regard, we analyze the entropic uncertainty, entropic uncertainty lower bound, and concurrence dynamics in two non-interacting qubits. The exposure of two qubits is studied in two different qubit-noise configurations, namely, common qubit-noise and independent qubit-noise interactions. To include the noisy effects of the local external fields, a Gaussian Ornstein–Uhlenbeck process is considered. We show that the increase in entropic uncertainty gives rise to the disentanglement in the two-qubit Werner state. Depending on the parameters adjustment and the number of environments coupled, different classical environments have varying capacities to induce entropic uncertainty and disentanglement in quantum systems. The entanglement remains vulnerable to the external classical fields; however, by employing the ideal parameter ranges we provided, prolonged entanglement retention while preventing entropic uncertainty growth can be achieved. Besides, we have also analyzed the intrinsic behavior of the classical fields towards two-qubit entanglement with no imperfection with respect to different parameters.

Quantum Mechanical Analysis Based on Perturbation Theory of CdSe/ZnS Quantum-Dot Light-Emission Properties.

A simulation of quantum dot (QD) energy levels was designed to reproduce a quantum mechanical analytic method based on perturbation theory. A Schrödinger equation describing an electron–hole pair in a QD was solved, in consideration of the heterogeneity of the material parameters of the core and shell. The equation was solved numerically using single-particle basis sets to obtain the eigenstates and energies. This approach reproduced an analytic solution based on perturbation theory, while the calculation was performed using a numerical method. Owing to the effectiveness of the method, QD behavior according to the core diameter and external electric field intensity could be investigated reliably and easily. A 9.2 nm diameter CdSe/ZnS QD with a 4.2 nm diameter core and 2.5 nm thick shell emitted a 530 nm green light, according to an analysis of the effects of core diameter on energy levels. A 4 nm redshift at V/cm electric field intensity was found while investigating the effects of external electric field on energy levels. These values agree well with previously reported experimental results. In addition to the energy levels and light emission wavelengths, the spatial distributions of wavefunctions were obtained. This analysis method is widely applicable for studying QD characteristics with varying structure and material compositions and should aid the development of high-performance QD technologies.

Thermoelectric properties and the effect of biaxial strain and external electric fields on the electronics of novel 2D Lace-like O-Pd2Q3 (Q= S, Se) monolayers

Inspired by the experimental synthesis of the novel 2D O-Pd2Se3 monolayer, we performed density functional theory calculations to reveal detailed investigations of the electronics, and thermal properties of 2D O-Pd2Q3 (Q= S, Se) monolayers. The O-Pd2S3 and Pd2Se3 are semiconductors with indirect band gaps of 0.43 eV and 0.33 eV, respectively. Through strain engineering, the bulk modulus B (N/m) and young's modulus Y (N/m) are also determined to acquire a deep understanding of the elasticity of the monolayers. We find that the bandgaps tend to increase with increasing tensile biaxial strain (+ε%), and decrease with increasing compressive biaxial strain (-ε%). In particular, the O-Pd2Se3 monolayer starts to manifest a metallic feature at -5%. More importantly, we note that at room temperature, and under biaxial strain, O-Pd2S3 (O-Pd2Se3) has a high electron (hole) carrier mobility up to ∼ 766 cm2 V−1 s−1 (∼ 106 cm2 V−1 s−1). We have also tuned the band gaps of the monolayers via the application of an external electric field, along the z-direction. We find that, in the [-2.5, +2.5] V/Å range, such external electric fields reduce the bandgaps in both monolayers, transforming Pd2Se3 into a metal at a strength of ± 2.5 V/Å. Additionally, we have perceived that the thermoelectric (TE) properties of these materials exhibit an anisotropic behavior at ambient and higher temperatures. At 300K, the O- Pd2Se3 monolayers show a large thermal electronic conductivity and a power factor of about 18 (16) times that of O-Pd2S3 along the x (y) directions. At temperatures higher than 600K, these properties become more dominant in O-Pd2S3. The acquired power factor of O-Pd2S3 (O-Pd2Se3) is much higher than that of the 1T phase of PdS2 (1T PdSe2 and penta-PdSe2). By just knowing the group velocities of the three acoustical modes, we were able to determine the minimum lattice thermal conductivity, which is 0.207 W/(m.K) for both systems. If properly exploited, these characteristics make the O-Pd2Q3 monolayers excellent candidates for the fabrication of novel ultrathin electronic and TE nanodevices at ambient and higher temperatures.