Strong Constant Magnetic Field Research Articles

ИСПОЛЬЗОВАНИЕ ОРТОГОНАЛЬНЫХ СИЛЬНЫХ ЭЛЕКТРИЧЕСКИХ И МАГНИТНЫХ ПОЛЕЙ ДЛЯ СОЗДАНИЯ ЧАСТОТНО-ПРЕОБРАЗОВАТЕЛЬНЫХ УСТРОЙСТВ АВТОДИННОГО ТИПА

In the framework of the drift-diffusion model of carrier transport in the bulk of III–V typesemiconductors, under external action of strong constant electric and magnetic fields orthogonallyoriented relative to each other, a new principle for applying the discovered effects is proposed, whichtake into account the nonlinearities of the output parameters of the working chip, which leads to thepossibility creation of new semiconductor structures controlled by a magnetic field (SSCMF). Previously,the diffusion component of the output current density was not taken into account as a separateeffect arising under the orthogonal action of strong electric and magnetic components, which was atfirst time considered in this paper. It is shown that this component is a part of the inductive transverseoutput current and can be considered as an independent effect. The proposed practical applicationis based on the classical relations that describe the component spatial representation of the effectivemass energy dependence and the parameters of the kinetic equations for the carriers drift andheating in the bulk of highly mobile III–V type semiconductors structures. (The energy dependence ofthe reciprocal effective mass value was obtained under the assumption that this parameter becomesheavier in the framework of the two-valley representation. However, the mechanism of such increasingis not considered in detail, but is taken into account as a result of expansion in a Taylor series.)At the same time, some new phenomena were also hypothetically discovered: a diffusion detectoreffect and a transverse induction effect controlled by a magnetic field, similar in its manifestation tothe Gunn effect observed in this direction. The results obtained open the prospect for creating fundamentallynew frequency-converting devices based on the above SSCMF, such as autodyne-type converters(mixers), one of the designs of which is also proposed in this work in a waveguide version. Inthe case of experimental confirmation of the discovered effects, which can be investigated using theblock diagram of the measuring setup proposed in the work, we can conclude that there are promisingnew applications of magnetically controlled semiconductor structures. In addition, equipmentdevelopers will be interested in the possibility of using the magnetic field orientation angle to controlthe output parameters of such structures as part of converters

Спектри власних хвиль плазмового твердотільного циліндра в сильному поздовжньому магнітному полі

Subject and Purpose. Eigenwave studies of various bounded structures make a prolific line of investigation in both modern radiophysics and solid-state and functional electronics. Conducting solids demonstrating plasma (semiconductor) properties attract particular attention. Owing to the high conductivity of semiconductors (as it is inversely proportional to the charge carrier effective mass that is smaller than the free electron mass), interest exists in propagation features of slow elliptical-polarization electromagnetic waves – helicons – in magnetized semiconductor waveguides. The present work aims to determine eigenwave spectra of a solid-state plasma cylinder in a strong constant concentric magnetic field. Methods and Methodology. The eigenwave theoretical study of a magnetoplasma cylinder in the free space is conducted in terms of Maxwell's equations. The motion equation of conduction electrons of a solid-state plasma is adopted with quasi-stationarity electromagnetic field conditions satisfied. The collision frequency of majority charge carriers is assumed substantially less than their cyclotron frequency. Results. The dispersion equation of a cylindrical solid-state plasma (semiconductor) waveguide has been obtained. It has been shown that a collisionless magnetoplasma waveguide supports propagation of bulk and surface helicons. The propagation is accompanied by the surface current flowing lengthways cylinder components. Charged particle collisions destroy the surface current and initiate additional (to helicons) H-type hybrid waves such that their phase velocities coincide with phase velocities of the helicons. It has been found that the nonreciprocity effect holds for the waveguide eigenwaves having identical field distribution structures but different azimuthal propagation directions, and it also does as soon as the external magnetic field changes its sense. Conclusion. The research results have deepened our understanding of physical properties of bounded structures with plasma-like filling media. More systematization has been added to the knowledge of eigenwave behavior of these structures in a quasi-stationarity electromagnetic field.

Di-lepton production from a single photon in strong magnetic fields: vacuum dichroism

We study di-lepton production from a single photon in the presence of a strong constant magnetic field. By the use of the Ritus-basis formalism, we analytically evaluate the photon-to-di-lepton conversion vertex with fully taking into account the non-perturbative interactions between the produced fermions and the strong magnetic field. We show that the di-lepton spectrum becomes anisotropic with respect to the magnetic-field direction and depends on the photon polarization as a manifestation of the vacuum dichroism in a strong magnetic field. According to the energy conservation in the presence of the Landau quantization, not only the transverse momentum of the produced fermions but also the longitudinal momentum is discretized, and the di-lepton spectrum exhibits spike structures as functions of the incident photon energy and the magnetic field strength. We also show that the di-lepton production is strictly prohibited for massless fermions in the lowest Landau levels as an analogue of the so-called helicity suppression.

Fourth-order energy-preserving exponential integrator for charged-particle dynamics in a strong constant magnetic field

Charged-particle dynamics in a strong constant magnetic field can yield a fast gyromotion with high frequency around the center. Considering the superior of exponential integrators for highly oscillatory problems and the benefit of energy preservation of numerical integrators in solving the charged-particle dynamics, this paper is devoted to developing a fourth-order energy-preserving exponential integrator for the charged-particle dynamics in a strong constant magnetic field. To this end, we first rewrite the problem in the form of a semilinear Poisson system, to which the exponential average vector field (EAVF) method can be applied with energy preservation. Then, by deriving the truncated modified differential equation of the EAVF method, we propose a fourth-order energy-preserving exponential integrator according to the modifying integrator theory. Finally, numerical results soundly support the good energy preservation and high efficiency of the proposed fourth-order integrator in solving the problem considered in this paper.

Magnetic billiards: Non-integrability for strong magnetic field; Gutkin type examples

We consider magnetic billiards under a strong constant magnetic field. The purpose of this paper is two-folded. We examine the question of existence of polynomial integral of billiard magnetic flow. As in our previous paper (Bialy and Mironov, 2016) we succeed to reduce this question to algebraic geometry test on existence of polynomial integral, which shows polynomial non-integrability for all but finitely many values of the magnitude. In the second part of the paper we construct examples of magnetic billiards which have the so called δ-Gutkin property, meaning that any Larmor circle entering the domain with angle δ exits the domain with the same angle δ. For ordinary Birkhoff billiard in the plane such examples were introduced by E. Gutkin and are very explicit. Our construction of Gutkin magnetic billiards relies on beautiful examples by F.Wegner of the so called Zindler curves, which are related to the problem of floating bodies in equilibrium, which goes back to S.Ulam (Problem 19 in The Scottish Book, 1981). We prove that Gutkin magnetic billiard can be obtained as a parallel curve to a Wegner curve. Wegner curves can be written by elliptic functions in polar coordinates so the construction of magnetic Gutkin billiard is rather explicit but much more complicated.

Gravitational Hertz experiment in dielectrics, excited by intense laser pulses

The possibility of generating and detection of high-frequency gravitational waves based on parametric optical processes in dielectric media excited by intense laser emission is analyzed. The theory predicts the feasibility of the Hertz gravitational laboratory experiment in dielectric media at the presence of strong constant magnetic field with illumination of this media by intense ultra short laser pulses of visible or ultraviolet ranges. Parametric conversion of ultra short intense laser pulses with frequency ω0 to a gravitational wave with frequency ωg=2ω0 and reconversion process of gravitational radiation to optical radiation at resonance condition for some dielectrics and photonic structures are predicted

Heavy quark complex potential in a strongly magnetized hot QGP medium

We study the effect of a strong constant magnetic field, generated in relativistic heavy ion collisions, on the heavy quark complex potential. We work in the strong magnetic field limit with the lowest Landau level approximation. We find that the screening of the real part of the potential increases with the increase in the magnetic field. Therefore, we expect less binding of the $ Q\bar{Q} $ pair in the presence of a strong magnetic field. The imaginary part of the potential increases in magnitude with the increase in the magnetic field, leading to an increase of the width of the quarkonium state with the magnetic field. All of these effects result in the early dissociation of $ Q\bar{Q} $ states in a magnetized hot quark-gluon plasma medium.

Классические модели ЯМР спектра

NMR dipolar spectrum formation is considered for spin system under strong constant and uniform magnetic field. Numerical simulation of system dynamics uses 125 magnetic moments are in cube 5×5×5. The response on jump of longitudinal external field is simulated. Free induction decay lasts dirung spin-spin relaxation time, while the longitudinal magnetization also jumps. Fourier spectra of magnetization signals include the peaks near zero, Larmor and double-Larmor frequencies. It corresponds well with the quantum theory of magnetic resonance. The Heisenberg equations for spin deviation from saturation state are transformed into continuum magnetization equations. It takes into account the non-secular terms in dipolar Hamiltonian. Final nonlinear system permits the standing monochromatic wave solution. It also reproduces three main peaks in NMR spectrum.

Exact energy levels and eigenfunctions of an electron on a nanosphere under the influence of a radial magnetic field

The exact energy levels and wave functions of an electron that is free to move on a nanosphere under the influence of a radial magnetic field have been determined. The wave functions are expressed in terms of Jacobi polynomials that are well defined and orthogonal and can be expressed using recurrence relations and series expansions. We also discuss the wave functions and energy levels in the presence of a very high magnetic field. Landau energy levels are shown for strong constant magnetic fields occurring on two-dimensional flat surfaces, if the radius is very large. The results are compared with those of previously published researches.

Averaging of nonlinear Schrödinger equations with strong magnetic confinement

We consider the dynamics of nonlinear Schrodinger equations with strong constant magnetic fields. In an asymptotic scaling limit the system exhibits a purely magnetic confinement, based on the spectral properties of the Landau Hamiltonian. Using an averaging technique we derive an associated effective description via an averaged model of nonlinear Schrodinger type. In a special case this also yields a derivation of the LLL equation.

Peierls substitution for magnetic Bloch bands

We consider the Schr\"odinger operator in two dimensions with a periodic potential and a strong constant magnetic field perturbed by slowly varying non-periodic scalar and vector potentials, $\phi(\epsilon x)$ and $A(\epsilon x)$, for $\epsilon\ll 1$. For each isolated family of magnetic Bloch bands we derive an effective Hamiltonian that is unitarily equivalent to the restriction of the Schr\"odinger operator to a corresponding almost invariant subspace. At leading order, our effective Hamiltonian can be interpreted as the Peierls substitution Hamiltonian widely used in physics for non-magnetic Bloch bands. However, while for non-magnetic Bloch bands the corresponding result is well understood, for magnetic Bloch bands it is not clear how to even define a Peierls substitution Hamiltonian beyond a formal expression. The source of the difficulty is a topological obstruction: magnetic Bloch bundles are generically not trivializable. As a consequence, Peierls substitution Hamiltonians for magnetic Bloch bands turn out to be pseudodifferential operators acting on sections of non-trivial vector bundles over a two-torus, the reduced Brillouin zone. Part of our contribution is the construction of a suitable Weyl calculus for such pseudos. As an application of our results we construct a new family of canonical one-band Hamiltonians $H^B_{\theta,q}$ for magnetic Bloch bands with Chern number $\theta\in \mathbb{Z}$ that generalizes the Hofstadter model $H^B_{\rm Hof} = H^B_{0,1}$ for a single non-magnetic Bloch band. It turns out that $H^B_{\theta,q}$ is isospectral to $H^{q^2B}_{\rm Hof}$ for any $\theta$ and all spectra agree with the Hofstadter spectrum depicted in his famous black and white butterfly. However, the resulting Chern numbers of subbands, corresponding to Hall conductivities, depend on $\theta$ and $q$, and thus the models lead to different colored butterflies.

ВЛИЯНИЕ СИЛЬНОГО МАГНИТНОГО ПОЛЯ НА ПРОЦЕССЫ ВОЗВРАТА В КРИСТАЛЛИЧЕСКИХ СПЛАВАХ И КРИСТАЛЛИЗАЦИИ В АМОРФНЫХ СПЛАВАХ НА ОСНОВЕ ЖЕЛЕЗА

The paper covers the study of the issue of the structure forming in the process of annealing affected by the strong magnetic field in the iron-base alloys. Such surveys became rather significant in recent years, as the specifying of mechanisms of strong magnetic fields interaction with the processes taking place in solid bodies is very topical from both the fundamental and the practical points of view. Despite the activity of the researchers and the availability of a number of works, this issue remains open to the present time, and the information and the explanation given in scientific literature contradict one another very often. The paper gives experimental data obtained in the result of specimens annealing under the conditions of the strong constant magnetic field of 6, 10 and 20 T. During the annealing, the processes of recovery of cold-rolled deformed Fe-3 % Si and Fe-50 % Ni alloys. The authors studied the structure, the magnetic properties, and the microhardness and determined that the magnetic field delays the recovery processes in the crystalline deformed alloys and causes the formation of nucleuses with the easy direction of magnetization. It is associated first with the magnetic field influence on the motion of dislocations. Moreover, the authors carried out the crystallization of Fe 81 Si 7 B 12 amorphous alloy produced by quenching on the drum. In amorphous alloys, the crystallization in the conditions of strong magnetic field causes the increase in the produced grain size in comparison with the crystallization without the field. The authors have not determined any magnetic field influence on the alloys texture crystallized from amorphous state.

Properties of the lunar wake predicted by analytic models and hybrid‐kinetic simulations

AbstractAn approximate model derived by Hutchinson (2008a), describing the interaction between the solar wind and the Moon, is applied to describe plasma in the lunar wake. The model accounts for plasma entering the wake region from two tangent points around the Moon. Cylindrical geometry is assumed, along with a strong constant magnetic field, and fixed transverse velocity and temperature. Under these approximations two angle‐dependent equations for fluid flow are obtained, which can be solved using the method of characteristics to provide the density inside the wake region. It is demonstrated that the model valid under these assumptions provides excellent agreement with observations from the ARTEMIS mission and with large‐scale hybrid‐kinetic plasma simulations. The model provides a practical alternative to kinetic simulations and is generally useful for determining properties of the lunar wake under different solar wind conditions. It will be useful as well for predicting properties of the plasma environment around unmagnetized bodies that have not yet been visited by spacecraft.

Effect of Radial Temperature Gradient on the Stability of Magnetohydrodynamic Dean Flow in an Annular Channel at High Magnetic Parameter

The effect of a radial temperature gradient on the stability of Dean flow of an electrically conducting fluid in an annular channel is investigated. A strong constant magnetic field is imposed in the axial direction. Finite-difference method is used to solve the eigenvalue problem. For given values of gap width d, between the cylinders, and magnetic parameter Q, electrically nonconducting (NC) walls are found to be more destabilizing than perfectly conducting (PC) walls when the temperature parameter N < 0. This trend persists even for small positive values of N but when N (>0) exceeds a critical value depending on Q, PC walls are slightly more destabilizing than NC walls. The critical value of the radii ratio η (0 < η < 1) beyond which the first unstable mode becomes nonaxisymmetric is determined for various values of N and Q.

Scaling at chiral quantum critical points in two dimensions

We study the localization properties of electrons moving on two-dimensional bi-partite lattices in the presence of disorder. The models investigated exhibit a chiral symmetry and belong to the chiral orthogonal (chO), chiral symplectic (chS) or chiral unitary (chU) symmetry class. The disorder is introduced via real random hopping terms for chO and chS, while complex random phases generate the disorder in the chiral unitary model. In the latter case an additional spatially constant, perpendicular magnetic field is also applied. Using a transfer-matrix-method, we numerically calculate the smallest Lyapunov exponents that are related to the localization length of the electronic eigenstates. From a finite-size scaling analysis, the logarithmic divergence of the localization length at the quantum critical point at E=0 is obtained. We always find for the critical exponent \kappa, which governs the energy dependence of the divergence, a value close to 2/3. This result differs from the exponent \kappa=1/2 found previously for a chiral unitary model in the absence of a constant magnetic field. We argue that a strong constant magnetic field changes the exponent \kappa within the chiral unitary symmetry class by effectively restoring particle-hole symmetry even though a magnetic field induced transition from the ballistic to the diffusive regime cannot be fully excluded.

On viscous flow and azimuthal anisotropy of the quark–gluon plasma in a strong magnetic field

We calculate the viscous pressure tensor of the quark–gluon plasma in a strong magnetic field. It is azimuthally anisotropic and is characterized by five shear viscosity coefficients, four of which vanish when the field strength eB is much larger than the plasma temperature squared. We argue that the azimuthally anisotropic viscous pressure tensor generates the asymmetric transverse flow. As an illustration, we consider non-relativistic plasma flow in a very strong constant magnetic field; azimuthal asymmetry in this case is as large as 1/3, even not taking into account the collision geometry. This result suggests that the magnitude of the shear viscosity extracted from the experimental data ignoring the magnetic field must be underestimated, although a more quantitative estimate warrants further numerical investigation.

Nonlinear stability of the ideal magnetohydrodynamic interchange mode at marginal conditions in a transverse magnetic field

The stability of the ideal magnetohydrodynamic (MHD) interchange mode at marginal conditions is studied. A sufficiently strong constant magnetic field component transverse to the direction of mode symmetry provides the marginality conditions. A systematic perturbation analysis in the smallness parameter, |b2/Bc|1/2, is carried out, where Bc is the critical transverse magnetic field for the zero-frequency ideal mode and b2 is the deviation from Bc. The calculation is carried out to third order including nonlinear terms. It is shown that the system is nonlinearly unstable in the short wavelength limit, i.e., a large enough perturbation results in instability even if b2/Bc > 0 (linearly stable). The normalized amplitude for instability is shown to scale as |b2/Bc|1/2. A nonlinear, compressible, MHD simulation is done to check the analytic result. Good agreement is found, including the critical amplitude scaling.

Instability of magnetohydrodynamic flow in an annular channel at high Hartmann number

Instability of a flow of an electrically conducting fluid in an annular channel is analyzed. Strong constant magnetic field is imposed in the axial direction. Similarly to toroidal duct experiments, the flow is driven by the azimuthal Lorentz force resulting from the interaction between the magnetic field and the radial electric currents created by a difference of electric potential imposed between the cylinders. The instability of the base flow, while clearly of centrifugal nature, is significantly different from the Dean instability detected earlier in hydrodynamic systems and similar MHD systems at low and moderate magnetic fields. Growing perturbations are oscillating and axisymmetric and consist of counter-rotating toroidal vortices arranged side by side in the radial direction and having meridional cross-sections in the form of elongated ellipses oriented slightly obliquely to the axial direction. Simulations of the secondary flow show an interesting feature of periodic transitions between two symmetric solutions.

H2 molecule in strong magnetic fields

The Pauli Hamiltonian of a molecule with fixed nuclei in a strong constant magnetic field is asymptotic, in norm-resolvent sense, to an effective Hamiltonian which has the form of a multi-particle Schrödinger operator with interactions given by one-dimensional δ-potentials. We study this effective Hamiltonian in the case of the H2 molecule and establish the existence of the ground state. We also show that the inter-nuclear equilibrium distance tends to 0 as the field strength tends to infinity.

The crystallization mode influence and magnetic field action upon the mechanical and thermal properties of composite materials on the basis of polymers and magnetic additives

The results of investigations of the temperature-time mode of the crystallization influence and magnetic field action upon the mechanic strength, magnetic permeability, and thermal properties of composites on the basis of polymers (PEHD, PVDF) and the magnetic additive BaO(Fe2O3)6 have been presented. It has been shown that the changes of the mechanical strength, magnetic permeability, and the thermal properties of the magnetic composites being studied, with regard to the temperature-time mode of crystallization and processing in a strong constant magnetic field, can be interrelated with the change of the polymer matrix supermolecular structure, the degree of the phase interaction, and the interphase layer thickness.