Dynamics of a wave packet in a system with a quantum dot in the Coulomb blockade regime

The nonstationary problem of electron tunneling through a quantum dot in the Coulomb block-ade regime is studied. The temporal Schrödinger equation is solved and the dynamics of the wave packet in a system consisting of a quantum dot connected to two one-dimensional contacts is investigated. The transmission coefficient is calculated. Dependences of the transmission on the tunneling electron energy are constructed.     

Electron conductance in curved quantum structures

A differential-geometry analysis is employed to investigate the transmission of electrons through a curved quantum-wire structure. Although the problem is a three-dimensional spatial problem, the Schrödinger equation can be separated into three general coordinates. Hence, the proposed method is computationally fast and provides direct (geometrical) parameter insight as regards the determination of the electron transmission coefficient. We present, as a case study, calculations of the electron conductivity of a helically shaped quantum-wire structure and discuss the influence of the quantum-wire centerline radius of curvature and pitch length for the conductivity versus the chemical potential.     

On the transmission coefficient for the double delta-function potential embedded in a crystalline lattice

The solution of the Schrödinger–Wannier equation is examined for the potential that is defined as a sum of the two delta functions of unequal strengths. The analytical expression for the transmission coefficient is derived from the solution. The transmission coefficient is shown to exhibit maxima and minima. Moreover, it is proved that the transmission coefficient in its maxima is larger and in its minima is smaller than the transmission coefficient for the corresponding single delta-function potential. Some differences between the transmission coefficient of particles with the quadratic energy spectrum and the transmission coefficient of particles with the Kane energy spectrum are presented.     

对称双势垒量子阱中自旋极化输运的时间特性

电子的隧穿时间是描述量子器件动态工作范围的重要指标. 本文考虑k³ Dresselhaus 自旋轨道耦合效应对系统哈密顿量的修正, 结合转移矩阵方法和龙格-库塔法来解含时薛定谔方程, 进而讨论了电子在非磁半导体对称双势垒结构中的透射系数及隧穿寿命等问题. 研究结果发现:由于k³ Dresselhaus 自旋轨道耦合效应使自旋简并消除, 并在时间域内得到了表达, 导致自旋向上和自旋向下电子的透射峰发生了自旋劈裂; 不同自旋取向的电子构建时间和隧穿寿命不同, 这是导致自旋极化的原因之一; 电子的自旋极化在时间上趋于稳定. 关键词： 自旋极化输运 透射系数 隧穿寿命 自旋极化率     

Ballistic electron transport in wrinkled superlattices

Inspired by the problem of elastic wave scattering on wrinkled interfaces, we studied the scattering of ballistic electrons on a wrinkled potential energy region. The electron transmission coefficient depends on both wrinkle amplitude and periodicity, having different behaviors for positive and negative scattering potential energies. For scattering on potential barriers, minibands appear in the electron transmission, as in superlattices, whereas for scattering on periodic potential wells the transmission coefficient has a more complex form. Besides suggesting that tuning of electron transmission is possible by modifying the scattering potential via voltages on wrinkled gate electrodes, our results emphasize the analogies between ballistic electrons and elastic waves even in scattering problems on non-typical configurations.     

Reconstruction of the order parameter of oriented liquid crystal droplets

An optical method is proposed to reconstruct the order parameter for liquid crystal droplets with rigidly fixed poles. The method is based on measurements of the coherent transmission coefficient of a oneatom layer (monolayer) of polymer-dispersed liquid crystal droplets and on comparison with the results of the solution of the direct problem. In solving the direct problem for determining the coherent transmission coefficient of the polymer-dispersed liquid crystal monolayer, the anomalous diffraction approximation and the approximation of the effective refractive indices for liquid crystal droplets were used. The capabilities of the method are illustrated by the reconstruction of one component of the diagonal tensor of the droplet order parameter.     

Transmission tomography of proportional scattering media

Reconstruction of the extinction coefficient spatial distribution in transmission tomography of proportional scattering media (PSM) is considered. An exact analytical solution to the transport equation for PSM is derived for an arbitrary distribution of radiation sources. An inverse problem of tomography as applied to PSM is solved exactly without making additional assumptions. Difficulties associated with implementation of the tomographic algorithm and with uncertain knowledge of the proportionality coefficient in PSM are discussed. The results obtained may be useful in designing new types of transmission optical tomographs.     

Transmission of microwaves through magnetoactive plasma

The possibility of transmission of microwaves through the plasma layer with an electron concentration of more than critical value is considered. The problem is solved by consideration of the interaction of a microwave with the plane layer of magnetoactive plasma. The problem is formulated by such a way as to obtain the estimation of the greatest lower bound of microwave transmission coefficient through the plasma layer. The results of numerical parametric investigations are applied for the transparency conditions of the shock wave plasma in space communication. The possibility of stable (without interruptions) microwave communication through the shock wave plasma is demonstrated     

Formation of silicon nanospheres in molten aluminum

Transmission electron microscopy and electron diffraction data show that, as silicon dissolves in molten aluminum, a great number of silicon nanospheres (from 1.5 nm to several tens of nanometers across) forms in the melt. When these particles are dissolved in toluene, the solution takes on a pale pink color and its transmission coefficient at a wavelength of 300 nm decreases fivefold. In such a solution, a great number of equal-size silicon nanospheres (1.5 nm in diameter) are observed.     

Transport in the two-terminal aharonov-bohm ring

The transmission coefficient of a nanodevice—a quantum ring with two one-dimensional conductors attached—is found. The Hamiltonian of a nanodevice is constructed in terms of the theory of self-adjoint extensions of symmetric operators. It is shown that, in this case, the transmission coefficient coincides with that determined by the Feynman sum rule for the probability amplitudes. The transmission coefficient of the nanodevice is studied as a function of the electron energy, magnetic field, and the relative positions of the conductor contacts and the ring.     

Simulation of transmission coefficient through a triangular potential barrier

An analytical expression of the transmission coefficient for the electron transport through a triangular potential barrier has been modified for solution using the method of numerical simulation. The triangular potential barrier has been modelled as a staircase function. The performance of this numerical simulation method is briefly described. The simulation has been developed for personal computer IBM PC AT.     

含δ势垒的铁磁/半导体/铁磁异质结中的自旋输运和渡越时间

研究了含δ势垒的铁磁/半导体/铁磁异质结中自旋相关的透射概率和渡越时间,讨论了量子尺寸效应和Rashba自旋轨道耦合效应对隧穿特性的影响.研究结果表明：δ势垒的存在降低了自旋电子的透射概率,改变了透射概率的位相.Rashba自旋轨道耦合强度的增加加大了透射概率的振荡频率.不同自旋取向的电子隧穿异质结时,渡越时间随着半导体长度、Rashba自旋轨道耦合强度以及两铁磁电极中的磁化方向的夹角的变化而变化. 关键词： δ势垒')" href="#">δ势垒 铁磁/半导体/铁磁异质结 Rashba自旋轨道耦合效应 渡越时间     

GaN真空面电子源光电发射机理研究

采用Cs源持续、O源断续的交替方法成功激活了GaN光电阴极,原位测试了透射模式下的光谱响应曲线,获得了透射模式下高达13%的量子效率.从一维定态薛定谔方程入手,得到了GaN真空面电子源材料的电子透射系数的表达式.对于一定形状的阴极表面势垒,电子透射系数决定于入射电子能量、表面势垒的高度和宽度.根据具有负电子亲和势(NEA)特性的透射式GaN光电阴极的能带及Cs,O覆盖过程中阴极表面势垒的变化情况,结合双偶极层[CaN(Mg):Cs]:O-Cs表面模型,分析了GaN真空面电子源材料NEA特性的形成原因.研究表明:Cs,O激活过程中形成的双偶极层对电子逸出起促进作用,双偶极层的形成是材料表面真空能级下降的原因. 关键词： GaN 电子源 透射系数 双偶极层     

Diffraction ofH 10 wave by inductive rod in dielectric layer

A rigorous solution is obtained for the problem of H₁₀-wave diffraction by an ideally conducting circular cylinder located in a dielectric layer parallel to the lateral walls of the waveguide. The absolute value and phase of the transmission coefficient of the system are studied as functions of the waveguide parameters. Total transmission and reflection of the incident are observed.Georigian Polytechnic Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 9, pp. 1050–1060, September, 1991.     

铁磁/半导体/铁磁结构的双量子环自旋输运的特性

研究了与铁磁/半导体/铁磁结构相关的双量子环自旋输运的规律,研究结果表明：总磁通为零条件下,铁磁电极磁化方向反平行时,双量子环与单量子环相比提高了自旋电子透射概率的平均值.铁磁电极磁化方向平行时,双量子环对提高自旋向下电子平均透射概率的效果更明显;双量子环受到Rashba自旋轨道耦合作用影响时,自旋电子的平均透射概率明显高于单量子环,即使再加上外加磁场的影响,透射概率较高这一特征依然存在;双量子环所含的δ势垒具有阻碍自旋电子输运的作用,随δ势垒强度Z的增大透射概率 关键词： 双量子环 Rashba自旋轨道耦合 透射概率 δ势垒')" href="#">δ势垒     

双stub介观环结构中的电子输运特征

采用量子波导理论研究了双stub介观环结构中电子输运特性。结果表明电子透射系数随stub的长度和环的大小而周期地振动,对环的周长和stub的长度做适当的调整,能使电子输运达到100%。并且比较了单stub介观环结构和双stub介观环结构对电子输运的影响,发现双stub的介观环结构对电子输运调制要比单stub介观环结构好。理论研究不仅对基础物理而且对量子器件研究均有重要意义。     

Theories of electrons in one-dimensional disordered systems

A critical survey of the literature on the theory of electronic states in, and electron transmission through, models of one-dimensional disordered solids and liquids is given in the first part. Reference to work on three-dimensional systems is included, especially where exact results have been obtained. The relationship between this subject and the problem of elastic vibrations in disordered solids is pointed out. A complete exposition of the authors' work on one-dimensional conductivity is then presented. It provides a rigorous solution of the problem of average resistance, and of the variance (fluctuations) of resistance, for important classes of disorder which are carefully and precisely defined. Conclusions regarding the role of disorder with respect to the transmission properties are presented and discussed. It is also pointed out that, with appropriate modifications, the results apply generally to wave propagation in inhomogeneous media.     

Quasi-linear stage of synchrotron instability I. The limit of low initial radiation energy density

We consider the initial problem of quasi-linear relaxation of synchrotron instability in a spatially homogeneous system of relativistic electrons embedded in a cold plasma. We analyze evolution of the energy spectrum of electrons and the frequency spectrum of radiation at the limit of low initial radiation energy density. At this limit, the problem is reduced to the solution of a diffusion equation with a stationary diffusion coefficient for the electron distribution over momentum which does not depend on the initial radiation energy density. The radiation frequency spectrum is approximated by the Gaussian profile, and its parameters are expressed via the electron energy density at the given and initial instants of time. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 11, pp. 964–976, November 2006.     

Test of rate theory transmission coefficient algorithms. An application to ion channels

The determination of rate constants is an important problem in many areas of chemical physics. Transition state theory (TST) is often used in estimating the rate constants. However TST neglects recrossings of the transition state by the reaction coordinate. The transmission coefficient is a correction to the TST estimate which accounts for the influence of recrossing dynamics. The transmission coefficient is calculated by generating activated trajectories which cross the transition state. This article investigates the correctness and efficiency of several current numerical algorithms for estimating the transmission coefficient, as well as a new one presented here. We use these algorithms to estimate the transmission coefficient for K⁺ diffusion through a model inward rectifier potassium (IRK1) ion channel.     

Measurement of the isotope composition of hydrogen in carbon materials using elastically scattered electron peak spectroscopy

The quantitative composition of hydrogen and helium isotopes in the surface layers of structural materials is reconstructed using the developed technique for processing the energy spectra of electrons scattered from plane-parallel layers of solids into a preset solid angle element. These are the spectra measured with a high energy resolution ΔE ∷ 0.2−0.4 eV. The change in the shape of peaks for elastically scattered electrons is analyzed depending on the probe electron beam energy and experimental geometry. The theory of electrons scattered from plane-parallel layers of solids is constructed using the solution of the boundary value problem for the transfer equation by invariant immersion methods. The analytic solution to the system of equations is found in the small-angle approximation for the reflection and transmission functions. The results of calculations are compared with experimental data on electron scattering from polyethylene. The shape of the energy spectra of electron scattering from deuterium and tritium is predicted. The sensitivity threshold of the method relative to percentage concentration of hydrogen isotopes in hydrocarbons is analyzed.