Constant External Magnetic Field Research Articles

Tunnel transport problem for open multilayer nitride nanostructures with an applied constant magnetic field and time-dependent potential: An exact solution

A quantum mechanical theory for description of electronic quasistationary states in two-dimensional (2D) layered semiconductor nanostructure was developed. A constant external magnetic field B was directed along semiconductor layers. The presence of internal electric fields F originated from the potential barriers and wells in semiconductor layers was taken into account. The vector of F was directed perpendicularly to semiconductor layers. The interaction of tunneled electrons with a time-dependent electromagnetic fields was analyzed in detail. An approach to obtain an exact solution to the problem based on a combination of the Lewis-Riesenfeld method for complete Schrödinger equation and scattering theory was developed. Application of the scattering theory in combination with the -matrix and transfer-matrix methods allowed us to calculate the electron quasistationary spectra. Effects of magnetic field on the resonant energy and width of electronic quasistationary states as well as on the electronic conductivity were also discussed. Published by the American Physical Society 2024

Rotation Matrix of a Charged Symmetrical Body: One-Parameter Family of Solutions in Elementary Functions

Euler–Poisson equations of a charged symmetrical body in external constant and homogeneous electric and magnetic fields are deduced starting from the variational problem, where the body is considered as a system of charged point particles subject to holonomic constraints. The final equations are written for the center-of-mass coordinate, rotation matrix and angular velocity. A general solution to the equations of motion is obtained for the case of a charged ball. For the case of a symmetrical charged body (solenoid), the task of obtaining the general solution is reduced to the problem of a one-dimensional cubic pseudo-oscillator. In addition, we present a one-parametric family of solutions to the problem in elementary functions.

Probing the interference between non-linear, axionic and space-time-anisotropy effects in the QED vacuum

In this paper, we pursue the investigation of a generic non-linear extension of axionic electrodynamics in a Carroll-Field-Jackiw (CFJ) scenario that implements Lorentz-symmetry violation (LSV). The model we inspect consists of an arbitrary non-linear electrodynamic action coupled to the axion field in presence of an anisotropy four-vector that realizes the breaking of Lorentz symmetry under the particle point of view. For the sake of our considerations, the non-linear electromagnetic field is expanded around a constant and uniform magnetic background up to second order in the propagating photon field. The focus of our attention is the study of the material properties of the vacuum in the particular case of a space-like CFJ 4-vector. The dispersion relations associated to the plane wave solutions are explicitly worked out in two situations: the magnetic background perpendicular and parallel to the wave direction. We extend these results to consider the analysis of the birefringence phenomenon in presence of non-linearity, the axion and the LSV manifested through the spatial anisotropy. Three specific proposals of non-linear electrodynamics are contemplated: Euler-Heisenberg (EH), Born-Infeld (BI) and the Modified Maxwell electrodynamics (ModMax). Throughout the paper, we shall justify why we follow the unusual path of connecting, in a single Lagrangian density, three pieces of physics beyond the Standard Model, namely, non-linearity, axions and LSV. We anticipate that we shall not be claiming that the simultaneous introduction of these three topics beyond the Standard Model will bring new insights or clues for the efforts to detect axions or to constrain parameters associate to both non-linear electrodynamics and LSV physics. Our true goal is to actually inspect and describe how axionic, non-linear and LSV effects interfere with one another whenever physical entities like group velocity, refraction indices, birefringence and effective masses of physical excitations are computed in presence of an external constant and homogeneous magnetic field.

Fermionic condensate and the vacuum energy-momentum tensor for planar fermions in homogeneous electric and magnetic fields

We consider a massive fermionic quantum field localized on a plane in external constant and homogeneous electric and magnetic fields. The magnetic field is perpendicular to the plane and the electric field is parallel. The complete set of solutions to the Dirac equation is presented. As important physical characteristics of the vacuum state, the fermion condensate and the expectation value of the energy-momentum tensor are investigated. The renormalization is performed using the Hurwitz function. The results are compared with those previously studied in the case of zero electric field. We discuss the behavior of the vacuum expectation values in different regions for the values of the problem parameters. Applications of the results include the electronic subsystem of graphene sheet described by the Dirac model in the long-wavelength approximation.

The influence of quark anomalous magnetic moment in the Nambu–Jona‐Lasinio model with different regularizations

AbstractThe Nambu–Jona‐Lasinio model is known for its simplicity and capacity to reproduce some of the basic characteristics of the quantum chromodynamics phase diagram. However, since it is a nonrenormalizable model, there are regularization issues that should be treated conveniently. This is the case when considering the quark anomalous magnetic moment (AMM) when external constant magnetic fields are present. Regularization procedures based on entangled functions between the magnetic field and the cutoff of the model can predict first‐order phase transitions for chiral symmetry restoration at finite values of magnetic fields and inverse magnetic catalysis. The strengths of magnetic fields explored in NJL model and lattice QCD do not show first‐order phase transition. In the present work, we show that some of the previous results are regularization‐dependent effects and how to handle the divergences using the vacuum magnetic regularization scheme.

Field-free spin-orbit-torque switching of a single ferromagnetic layer with fourfold in-plane magnetic anisotropy

We present the observation of field-free spin-orbit-torque (SOT) switching of magnetization in a ferromagnetic semiconductor (Ga,Mn)As film with four-fold in-plane magnetic anisotropy. Magnetization switching is demonstrated between two orthogonal in-plane easy axes through planar Hall resistance measurements as a current is scanned in the absence of a magnetic field. The chirality of the switching of the current hysteresis loop is consistent with SOT arising from spin polarization caused by Dresselhaus- and Rashba-type spin-orbit-induced effective magnetic fields in the (Ga,Mn)As film. The chirality of magnetization switching can be reversed either by changing the direction of the initial magnetization or by applying a constant external magnetic field bias. The SOT magnetization switching between two states was consistently repeated by applying sequential current pluses with alternating polarities, indicating the potential for developing a field-free SOT device.

Magnetization measurements of multicomponent iron garnets

Magnetization studies were performed on four Gd-containing iron garnets. Measurements have been done in an external constant magnetic field as a function of temperature. A change in the orientation of magnetization was observed at the compensation temperature in measurements without an external magnetic field, and ranges of no dependence of magnetization on temperature around the compensation temperature in measurements in strong magnetic fields up to 9 T. The results were interpreted using crystal field approximation, and on this basis the magnetic moments of the particular elements as well as molecular field coefficients λij were determined.

FEATURES OF PERFORMING EXPERT STUDIES OF MAGNETIC FIELD INDICATORS AS A MEANS OF IDENTIFYING THE IMPACT ON METERING DEVICES OF AN EXTERNAL MAGNETIC FIELD CREATED FOR THE PURPOSE OF UNACCOUNTED CONSUMPTION OF ENERGY RESOURCES

The study of the facts and circumstances of the unaccounted use of energy resources by consumers, primarily electric energy, natural gas, hot and cold water in the practice of conducting electrical and heat engineering types of forensic examinations, is one of the most common. The initial data in forensic research in this area, namely the data of acts on the violation of the consumption of these energy resources, including information on fixing the impact on the metering device of a constant magnetic field by magnetic field effect indicator (MFEI), which in the cases under study is usually denied by the consumer as his intentional actions to create such a field. The expert task of forensic examinations in this area requires an unambiguous definition of the operation of a MFEI from a constant magnetic field with certain power characteristics, with the exclusion of other factors of influence. The most common modern designs of magnetic field impact indicators in use, which are installed by energy sales enterprises as fixing technical means of interfering with the operation of consumer metering devices when using energy resources as a result of exposure to an external constant magnetic field, are considered. The triggering mechanism of MFEI of different designs is analyzed. According to the constructive construction and principle of operation, the indicators of the influence of the magnetic field are divided into separate classification groups. Signs of atypical triggering of the MFEI are considered. Cases of activation of indicators of the impact of the magnetic field are determined, requiring a comprehensive study using research methods of various forensic specialties to establish the fact of interference in the operation of metering devices in order to unaccounted for the consumption of energy resources. Recommendations are given on the application of the method of modeling a constant magnetic field with the reproduction of the conditions for the operation of the investigated MFEI to establish the fact of interference in the operation of the meter by exposing it to an external constant magnetic field in order to unaccounted for the consumption of energy resources. The necessity of performing a check of the operable state of the MFEI in expert experience in the study of the fact of the existence of the influence of a constant magnetic field on the metering device for energy consumption is substantiated.

A generalized More-Gibson-Thomson heat transfer model for the study of thermomagnetic responses in a solid half-space

In this article, thermomagnetic interactions in a two-dimensional (2D), isotropic, homogeneous, and thermoelastic infinite half-space are discussed. It was proposed to use an improved version of the Moore-Gibson-Thompson (MGT) model of thermoelasticity. Since the relaxation time was taken into account in the Green-Naghdi formulation, this model was established. In addition, Maxwell's equations of magnetic and electric fields were taken into account during the formulation of the governing equations. The surface of the solid is considered to be free of traction, under the influence of a varying temperature, and immersed in a constant external magnetic field. In order to solve the non-dimensional coupled magnetic-thermal equations, the normal mode analysis approach and the deletion method were employed. The effects of the magnetic field, thermal factors, and other parameters on the investigated field variables are illustrated graphically and analyzed. There was also a comparison made between the outcomes of the suggested system and those of other thermal frameworks that can be derived as special cases. The results show that the MGT model reduced the magnitudes of the analyzed variables, which may have significant ramifications for various real-world scenarios.

Effect of thermal radiation and nth order chemical reaction on non-Darcian mixed convective MHD nanofluid flow with non-uniform heat source/sink

The present perusal is to scrutinize the consequences of free-forced convective heat-mass transportation and n th order chemical reaction on MHD, non-Darcian, incompressible nanofluid fluid flow through an extended lamina, immersed in a permeable medium along with an external constant magnetic field. The fluid flow governing equations (PDEs) has been transformed into a system of nonlinear ODEs with the help of appropriate similarity transformation, and then solved numerically by using SQLM (Spectral quasilinearization method) method. Solution error for temperature and concentration profile against radiation parameter, Brownian motion parameter, and Hartman number also has been depicted diagrammatically. The graphical representation shows that the Hartman number, Brownian motion parameter, and chemical reaction parameter decline in velocity. While, the thermal boundary layer enhances with an enhancement of the Hartman number, Brownian motion parameter, radiation parameter, and chemical reaction parameter. Generation of entropy increases with the Brinkman number, Reynolds number, and Hartman number in the vicinity of the stretching lamina. Brinkman number and Reynolds number reduce the Bejan number. For the engineering interest Skin-friction, the local Nusselt number, and local Sherwood number also have been calculated. Impacts of pertinent parameters on the skin friction, Nusselt number, and Sherwood number are examined graphically and also numerically.

Mechanism of low-temperature helical streamer discharge driven by pulsed electromagnetic field

Under the condition of specific pulsed discharge parameters, the discharge mode conversion of the low-temperature plasma jet discharge channel that originally propagates along a straight line will occur, forming a three-dimensional helical plasma channel. Unlike the traditional helical wave discharge, there are no factors such as an external constant magnetic field that destroys the poloidal symmetry of the dielectric tube, and the chiral direction of the helical streamer will change with the discharge parameters. In order to understand in depth the electromagnetic mechanism of the helical structure in the plasma jet, and the source and influencing factors of the poloidal electric field that leads to the helical shape and determines the chirality in this new type of discharge, we analyze the complex characteristics and electromagnetic mechanism of the helical streamer, such as the chiral direction, pitch, branching, by establishing a self-consistent plasma theoretical model. It is found that the phase of the poloidal wave mode has an effect on the chiral selection of the helical streamer, that the electron density has an influence on the pitch of the streamer, and that the repetition frequency has an effect on the bifurcation point. The above discharge characteristics and their influencing factors are of scientific significance in exploring the interaction mechanism of electromagnetic wave and plasma, and also in providing experimental and theoretical support for the chiral application of low-temperature plasma.

The frequency of current fluctuations in two-valley semiconductors in an external electric and strong magnetic (

Boltzmann's kinetic equations have not been used to date to study nonequilibrium phenomena in semiconductors, and therefore, to obtain analytical expressions for the oscillation frequency inside the semiconductor and the critical external electric field, it is of theoretical interest. In this theoretical work, the frequency of oscillations occurring inside a two-valley semiconductor of the GaAs type in an external constant electric field and in an external strong magnetic field (

Stationary states of open XX -spin chains

We study an open quantum spin chain of arbitrary length with nearest neighbor $XX$ interactions of strength $g$, immersed in an external constant magnetic field $\mathrm{\ensuremath{\Delta}}$ along the $z$ direction, whose end spins are weakly coupled to two heat baths at different temperatures. In the so-called global approach, namely, without neglecting interspin interactions, using standard weak-coupling limit techniques, we first derive the open chain master equation written in terms of fermionic mode operators. Then, we focus on the study of the dependence of the resulting open dynamics from the ratio $r\ensuremath{\equiv}g/\mathrm{\ensuremath{\Delta}}$. By increasing $r$, some of the chain Bohr transition frequencies become negative; when this occurs, both the generator of the dissipative time evolution and its stationary states behave discontinuously. As a consequence, the asymptotic spin and heat flows also exhibit discontinuities, but in a different way: while source terms in the spin flow continuity equation show jumps, the heat flow instead is continuous but with discontinuous first derivatives with respect to $r$. These two behaviors might be experimentally accessible; in particular, they could discriminate between the global and the local approaches to open quantum spin chains. Indeed, the latter one, which neglects interspin interactions in the derivation of the master equation, does not show any kind of discontinuous behavior.

Stable, metastable and unstable states of the mixed spin (1, 3/2) Ising model in the absence and presence of constant magnetic fields

Stable, metastable and unstable states of the mixed spin (1, 3/2) Ising system in the absence and presence of constant external magnetic fields (CEMFs) were investigated both by the cluster variation method (CVM) and the path probability method (PPM). First, we examine the thermal behavior of the magnetizations by using the CVM and search the metastable and unstable branches of magnetizations in addition to the stable branches. We present the metastable phase diagrams besides to equilibrium phase diagrams in the absence of the CEMFs. We also constructed only the metastable phase diagram under the presence of CEMFs. Since the metastability is a stable state of a dynamical system, we used the PPM on the model and found the dynamic equations. Dynamic equations were solved by means of the flow diagrams (FDs). The FDs clearly display the stable, metastable and unstable states in which also obtained within the CVM. The FDs display the role of the metastable, unstable states and initial conditions as well as how the system trapped into the metastable state. Some properties of the metastable states were observed from the FDs. These studies were made both for the ferrimagnetic and antiferrimagnetic cases.PACS: 05.50. + q, 05.70.Fh, 05.70.Ln, 64.60.Cn, 64.60. My, 75.10.Hk

Tunable Faraday effect in Graphene/SiO2/Ta2O5 layered structure using a pump He-Ne laser light

Faraday rotation spectrum of a Graphene/SiO2/Ta2O5 layered structure under an external magnetic field and a pump light of a He-Ne laser with the wavelength of 632.8 nm is investigated in the THz frequency region. The results showed that, when the pump light is turned off and the magnetic field strength is increased, the maximum Faraday rotation angle frequency shifts toward the higher frequencies, as well as, the value of the maximum Faraday rotation angle increases. Furthermore, for a constant external magnetic field, by increasing the pump light power, the value of Faraday rotation increases, and the maximum Faraday rotation frequency shifts toward the lower frequencies. However, the noticeable changes in the transmission spectrum were not observed by changing the magnetic field strength and the pump light power. These results would have potential applications in designing the magneto-optical devices with tuning property of the Faraday rotation using a pump He-Ne laser.

Magnetic Self-Healing Composites: Synthesis and Applications.

Magnetic composites and self-healing materials have been drawing much attention in their respective fields of application. Magnetic fillers enable changes in the material properties of objects, in the shapes and structures of objects, and ultimately in the motion and actuation of objects in response to the application of an external field. Self-healing materials possess the ability to repair incurred damage and consequently recover the functional properties during healing. The combination of these two unique features results in important advances in both fields. First, the self-healing ability enables the recovery of the magnetic properties of magnetic composites and structures to extend their service lifetimes in applications such as robotics and biomedicine. Second, magnetic (nano)particles offer many opportunities to improve the healing performance of the resulting self-healing magnetic composites. Magnetic fillers are used for the remote activation of thermal healing through inductive heating and for the closure of large damage by applying an alternating or constant external magnetic field, respectively. Furthermore, hard magnetic particles can be used to permanently magnetize self-healing composites to autonomously re-join severed parts. This paper reviews the synthesis, processing and manufacturing of magnetic self-healing composites for applications in health, robotic actuation, flexible electronics, and many more.

Study of small perturbations of a stationary state in a model of upper hybrid plasma oscillations

It is shown that a constant external magnetic field, generally speaking, is not able to prevent breaking (loss of smoothness) of relativistic plasma oscillations, even if they are arbitrarily small perturbations of the zero steady-state. This result sharply differs from the non-relativistic case, for which it is possible to suppress the breaking of oscillations at any initial deviations by increasing the intensity of the magnetic field \cite {RCharx}. Nevertheless, even in the relativistic case, there are subclasses of solutions corresponding to solutions that are globally smooth in time.

Unified approach to cyclotron and plasmon resonances in a periodic two-dimensional GaAs electron gas hosting the Hofstadter butterfly

We present theoretical calculations for the cyclotron resonance and various magnetoplasmon modes of a Coulomb interacting two-dimensional GaAs electron gas (2DEG) modulated as a lateral superlattice of quantum dots subjected to an external perpendicular constant magnetic field. We use a real-time excitation approach based on the Liouville-von Neumann equation for the density operator, that can go beyond linear response delivering information of all longitudinal and transverse collective modes of interest to the same order. We perform an extensive analysis of the coexisting collective modes due to the lateral confinement and the magnetic field for a different number of electrons in each dot. In the limit of vanishing dot modulation of the 2DEG we find signs of the structure of the Hofstadter butterfly in the excitation spectra.

Magneto-Thermoelastic Response in an Unbounded Medium Containing a Spherical Hole via Multi-Time-Derivative Thermoelasticity Theories.

This article introduces magneto-thermoelastic exchanges in an unbounded medium with a spherical cavity. A refined multi-time-derivative dual-phase-lag thermoelasticity model is applied for this reason. The surface of the spherical hole is considered traction-free and under both constant heating and external magnetic field. A generalized magneto-thermoelastic coupled solution is developed utilizing Laplace’s transform. The field variables are shown graphically and examined to demonstrate the impacts of the magnetic field, phase-lags, and other parameters on the field quantities. The present theory is examined to assess its validity including comparison with the existing literature.

Position-space representation of charged particles\u2019 propagators in a constant magnetic field as an expansion over Landau levels

We have obtained propagators in the position space as an expansion over Landau levels for the charged scalar particle, fermion, and massive vector boson in a constant external magnetic field. The summation terms in the resulting expressions consisted of two factors, one being rotationally invariant in the 2-dimensional Euclidean space perpendicular to the direction of the field, and the other being Lorentz-invariant in the 1+1-dimensional space-time. The obtained representations are unique in the sense that they allow for the simultaneous study of the propagator from both space-time and energetic perspectives which are implicitly connected. These results contribute to the development of position-space techniques in QFT and are expected to be of use in the calculations of loop diagrams.