Transverse Thermomagnetic Effect in the Two-Dimensional Electron Gas of Surface Semiconductor Superlattice

Journal of Experimental and Theoretical Physics - The surface current density of charge carriers in two-dimensional doubly periodic n-type semiconductor superlattices in an external magnetic field...     

Compton scattering of 59.54 keV γ‐rays from Fe and p‐Si samples in an external magnetic field

We report on the Compton scattering of photons from samples whose surface charge density distributions are changed by an external magnetic field. We performed a Compton scattering experiment known to be particularly sensitive to the behavior of the relatively slower moving outer electrons (valence electrons) involved in bonding in condensed matter. The external magnetic field was used to change the surface charge density distributions of Fe and p‐Si samples. Samples were located in the external magnetic field of intensity 215 G and in a direction which was perpendicular both to the current and surface of the samples bombarded by 59.5 keV γ‐photons emitted from an Am‐241 point source. Currents in the ranges 0–8.5 A and 0–300 µA were applied to the Fe and p‐Si samples, respectively. The Compton scattered photons at an angle of 100° were detected by an Si(Li) detector. It was observed that the counts acquired under the Compton peaks tended to decrease linearly with increasing current in a magnetic field. The results show that positive charge carriers behave like negative charge carriers and electrons are more effective than holes in the Compton scattering of γ‐rays. Copyright © 2003 John Wiley & Sons, Ltd.     

Random acoustoelectric oscillations of current in piezoelectric semiconductors

The effect of the supersonic drift of charge carriers on phonon generation in tellurium crystals is studied under the conditions of the emergence of acoustic instability leading to dynamic chaos. All stages of the stochasticity evolution are traced experimentally with varying the external conditions, namely, the magnitude of the static electric field, determining the drift of charge carriers, and the magnitude and direction of the magnetic field. It is shown that with increasing electric and magnetic fields, the periodic oscillations of the current are transformed into random oscillations through the frequency-doubling and tripling bifurcations. A mathematical model in the form of phase trajectories of the dissipative dynamic system and the spectral portraits corresponding to transient processes are described.     

Thermoelectric effects in organic conductors in a strong magnetic field

The linear response of the electron system of a layered conductor to the temperature gradient in this system in a strong magnetic field is investigated theoretically. Thermoelectric emf is studied as a function of the magnitude and orientation of a strong external magnetic field; the experimental investigation of this function, combined with the study of the electric and thermal resistance, allows one to completely determine the structure of the energy spectrum of charge carriers.     

Gravitoelectric-electric coupling via superconductivity

Recently we demonstrated theoretically that the carriers of quantized angular momentum in superconductors are not the Cooper pairs but the lattice ions, which must execute coherent localized motion consistent with the phenomenon of superconductivity. We demonstrate here that in the presence of an external magnetic field, the free superelectron and bound ion currents largely cancel providing a self-consistent microscopic and macroscopic interpretation of near-zero magnetic permeability inside superconductors. The neutral mass currents, however, do not cancel, because of the monopolar gravitational charge. It is shown that the coherent alignment of lattice ion spins will generate a detectable gravitomagnetic field, and in the presence of a time-dependent applied magnetic vector potential field, a detectable gravitoelectric field.     

Books received

A new kind of experiment is described which measures the ‘effective mass’ of mobile electrons in semiconductors and metals. Samples are placed in a magnetic field which causes the charge carriers to move in circular paths, and a microwave oscillating electric field accelerates them in the same way as charged particles in a vacuum are accelerated in a cyclotron. The effective mass thus determined measures the momentum transfer between the crystal lattice and the electron waves and thus gives detailed information about the nature of the conduction electron states.     

Effects of electric field and magnetic induction on spin injection into organic semiconductors

Spin-polarized injection and transport into ferromagnetic/organic semiconductor structure are studied theoretically in the presence of the external electric field and magnetic induction. Based on the spin-drift-diffusion theory and Ohm's law, we obtain the charge current polarization, which takes into account the special carriers of organic semiconductors. From the calculation, it is found that the current spin polarization is enhanced by several orders of magnitude by tuning the magnetic induction and electric fields. To get an apparent current spin polarization, the effects of spin-depended interfacial resistances and the special carriers in the organic semiconductor, which are polarons and bipolarons, are also discussed.     

磁场对球头阴极二极管特性的影响

 采用全电磁PIC粒子模拟方法研究了磁场对球头阴极二极管物理特性的影响。结果表明外加磁场主要是通过对二极管束流轨迹的改变来影响二极管的物理特性。由于外加磁场将约束其产生电子束的发散，结果使其空间电荷限制电流减小，其值在无外加磁场并且自磁场可以忽略时的空间电荷限制电流值的0.5~1倍范围内。当外加磁场足够强时，束流轨迹主要受外加磁场控制，二极管产生的电子束既不箍缩也不发散。强外加磁场条件下的空间电荷限制电流近似为无外加磁场时的一半；在无外加磁场条件下，在阳极处的束流半径随二极管电压电流的增大而减小，空间电荷限制电流增强因子随束流半径的减小而减小，随二极管电压电流增大而减小。这一系列结果是在二极管电流小于其自箍缩临界电流条件下得到的。     

Nonlinearity of the zigzag graphene nanoribbons with antidots via the f-deformed Dirac oscillator in (2+1)-dimensions

We study the nonlinearity for the zigzag graphene nanoribbons (ZGNRs) with zigzag triangular holes (ZTHs). We show that in the presence of an external uniform magnetic field, a two-dimensional f-deformed Dirac oscillator can be used to describe the dynamics of the electrons in the ZGNRs with ZTHs. It is shown for the first time that the magnetic field direction has effect on the chirality of charge carriers in the ZGNRs punched with triangular holes. We also obtain the Landau-level spectrum in the weak and strong magnetic field regimes. Additionally, we compare Landau-level spectrum of this graphene-based device in the f-deformed scenario and original one. Our results provide a general viewpoint for the development of the zigzag graphene nanoribbons.     

Electro-optical transitions in a semiconductor cylindrical nanolayer

The single-electron states in a quantized cylindrical layer have been considered in the presence of a moderate homogeneous electric field, when the energy imparted to a charge carrier by the electric field becomes comparable to the energy of rotational motion of this particle. The corresponding energy spectrum and the envelopes of the wave functions of charge carriers in the layer have been obtained in an explicit form. The electro-optical absorption band of a weak electromagnetic wave has been calculated. It has been found that the absorption intensity increases with an increase in the intensity of the electric field. The external electric field leads to an explicit dependence of the absorption intensity on the effective masses of charge carriers. The absorption intensity decreases as the difference between the effective masses of charge carriers increases. There is also an effective broadening of the band gap, which is determined by the geometrical dimensions of the sample and the magnitude of the external field.     

Excitation of the spin density and current by coherent light pulses in quantum wells

We study the orbital and spin dynamics of charge carriers induced by non-overlapping linearly polarized light pulses in semiconductor quantum wells. It is shown that such an optical excitation with coherent pulses leads to a spin orientation of photocarriers and an electric current. The effects are caused by the interference of optical transitions driven by individual pulses. The distribution of carriers in the spin and momentum spaces depends on the crystallographic orientation of quantum wells and can be efficiently controlled by the pulse polarizations, time delay and phase shift between the pulses, as well as an external magnetic field.     

Optical absorption in a narrow-band InSb cylindrical layered nanowire in the presence of strong electrostatic field

On the example of InSb we consider the influence of a strong homogeneous electrostatic field on the state of carriers in a narrow-band quantized cylindrical layer in the case of Kaine dispersion law. Explicit expressions for the energy spectrum and wave function envelopes of charge carriers in the heterolayer are obtained. It is shown that under action of the strong external field the rotational motion, with respect to angular variables, of charge carriers becomes oscillatory in a narrow cone of the azimuth angle. We have obtained corresponding selection rules and calculated the threshold frequencies of absorption for interband and intraband electro-optical transitions in the layer. The threshold frequencies are determined by the geometric sizes of the sample and the magnitude of the external field.     

New method of the spin-polarization detection in tunnel junctions ferromagnet-insulator-charge density wave metal

A tunnel junction between a metal partially gapped by charge density waves metal (CDWM) and a ferromagnet (FM) in an external magnetic field is considered. Only the Zeeman paramagnetic effect is taken into account. It is shown that the peaks in the dependence of differential conductance versus voltage, induced by the CDW gap, split, with each peak having a predominant spin polarization. This effect makes it possible to electrically measure the polarization of current carriers in FMs.     

Principles of Adaptive Optics, 3rd edn., by Robert K. Tyson

A review is made of the quantum effects which are observed in the transport coefficients of semiconductors. Quantization of the free carriers in semiconductors is produced whenever an external potential acts on an otherwise uniform and perfect crystal. Typical examples are a magnetic field, an electric field or the physical boundaries of the sample. A magnetic field quantizes the electron and hole states into a ladder of equally spaced Landau levels. This gives rise to the Shubnikov–de Haas, magnetophonon and magneto-impurity effects, where the positions of the Landau levels resonate with the Fermi, phonon, or impurity energies present in the sample. A series of oscillations in the magneto-resistance of many different types of materials results. Electric fields applied to the surface of metal oxide semiconductor (MOS) devices result in a set of quantum levels for motion perpendicular to the surface. At low temperatures the charge carriers are bound to the surface and behave as if they were two-dimensional. This is shown to give rise to very dramatic oscillatory metal–insulator behaviour in high magnetic fields. Quantization is also shown to occur in very thin layers of semiconductors which act like a simple square well potential, the energy levels of which can be studied as a function of layer thickness. The carriers are confined within the layers, and also show two-dimensional behaviour.     

Magnetic response to applied electrostatic field in external magnetic field

We show, within QED and other possible nonlinear theories, that a static charge localized in a finite domain of space becomes a magnetic dipole, if it is placed in an external (constant and homogeneous) magnetic field in the vacuum. The magnetic moment is quadratic in the charge, depends on its size and is parallel to the external field, provided the charge distribution is at least cylindrically symmetric. This magneto-electric effect is a nonlinear response of the magnetized vacuum to an applied electrostatic field. Referring to the simple example of a spherically symmetric applied field, the nonlinearly induced current and its magnetic field are found explicitly throughout the space; the pattern of the lines of force is depicted, both inside and outside the charge, which resembles that of a standard solenoid of classical magnetostatics.     

Effect of external magnetic field on critical current for the onset of virtual cathode oscillations in relativistic electron beams

In this Letter we research the space charge limiting current value at which the oscillating virtual cathode is formed in the relativistic electron beam as a function of the external magnetic field guiding the beam electrons. It is shown that the space charge limiting (critical) current decreases with growth of the external magnetic field, and that there is an optimal induction value of the magnetic field at which the critical current for the onset of virtual cathode oscillations in the electron beam is minimum. For the strong external magnetic field the space charge limiting current corresponds to the analytical relation derived under the assumption that the motion of the electron beam is one-dimensional [D.J. Sullivan, J.E. Walsh, E. Coutsias, in: V.L. Granatstein, I. Alexeff (Eds.), Virtual Cathode Oscillator (Vircator) Theory, in: High Power Microwave Sources, vol. 13, Artech House Microwave Library, 1987, Chapter 13]. Such behavior is explained by the characteristic features of the dynamics of electron space charge in the longitudinal and radial directions in the drift space at the different external magnetic fields.     

均匀磁场中转动的导体上电荷的分布

指出了在均匀磁场中运动的轴对称导体上分布的电荷所产生的附加磁场是很弱的,在忽略附加磁场时导体内的电荷是均匀分布的,并求出导体球上电荷分布。     

In vitro investigation of the behaviour of magnetic particles by a circulating artery model

Magnetic drug targeting is the use of coated magnetic nanoparticles as carriers for cytostatic drugs. After intraarterial application of these carriers, they are attracted with an external magnetic field to, for example, an experimental VX2 tumour. The biological compatibility of this system depends on several physiological and physical parameters. We established an in vitro model to simulate in vivo conditions in a circulating system consisting of a circuit with an intact bovine femoral artery close to an external magnetic field. Nanoparticle suspensions were applied by a side inlet. After the magnetisation procedure particle size, concentration and distribution was examined.     

Electron and hole states in a narrow-band semiconductor InSb film in the presence of uniform electrostatic field

The states of charge carriers in a narrow-gap semiconductor InSb film, placed in a uniform electrostatic field, are considered theoretically. We consider the case when the heavy holes are described by the standard dispersion, and Kane’s dispersion law takes place for electrons and for light holes within the framework of two-band mirror model. For a certain range of values of the external field, explicit expressions for the energy spectrum and the envelope wave functions of charge carriers are obtained. Corresponding numerical estimations of allowed range of the external field are derived, for which the proposed approach allows exact analytical solutions.     

Spin Localization in Poly(3-Dodecylthiophen)/PCBM Composite

Charge carriers photoinduced in poly(3-dodecylthiophene)/([6,6]-phenyl-C₆₁-butanoic acid methyl ester) (P3DDT/PCBM) by photons with the energy of 1.88–2.75 eV were investigated by X-band light-induced electron paramagnetic resonance (LEPR). LEPR spectra were attributed to non-interacting polarons and methanofullerene anion radicals with different magnetic and relaxation parameters. A part of these charge carriers are trapped in a polymer matrix. Paramagnetic susceptibility and spin–spin relaxation of mobile charge carriers were shown to follow the activation law.