Photon tunneling and transmittance resonance through a multi-layer structure with a left-handed material

This paper investigates the photon tunneling and transmittance resonance through a multi-layer structure including a left-handed material(LHM).An analytical expression for the transmittance in a five-layer structure is given by the analytical transfer matrix method.The transmittance is studied as a function of the refractive index and the width of the LHM layer.The perfect photon tunneling results from the multi-layer structure,especially from the relation between the magnitude of the refractive index and the width of the LHM layer and those of the adjoining layers.Photons may tunnel through a much greater distance in this structure.Transmittance resonance happens,the peaks and valleys appear periodically at the resonance thickness.For an LHM with inherent losses,the perfect transmittance is suppressed.     

Photon tunneling and transmittance resonance through a multi-layer structure with a left-handed materialvspace2pt

This paper investigates the photon tunneling and transmittance resonance through a multi-layer structure including a left-handed material(LHM). An analytical expression for the transmittance in a five-layer structure is given by the analytical transfer matrix method. The transmittance is studied as a function of the refractive index and the width of the LHM layer. The perfect photon tunneling results from the multi-layer structure, especially from the relation between the magnitude of the refractive index and the width of the LHM layer and those of the adjoining layers. Photons may tunnel through a much greater distance in this structure. Transmittance resonance happens, the peaks and valleys appear periodically at the resonance thickness. For an LHM with inherent losses, the perfect transmittance is suppressed.     

The asymmetry of the tunneling time in type II semiconductor heterostructures

The tunneling time asymmetry in type II semiconductor heterostructures is related to the phase difference of the reflection coefficients for the two tunneling directions. Analytical expressions and numerical simulations are given for the difference between the left-to-right and right-to-left tunneling times in asymmetric, single and multiple barrier type II heterostructures.     

摇摆型棘齿热电子隧穿制冷

本文利用传输矩阵法数值模拟了电子在加入周期性正负偏压的双势垒("摇摆"棘齿)异质结中的传输特性,获得了两电子库间的净电流以及所伴随的净热流的表达式.进一步分析了净电流、净热流和制冷系数等性能参数的特征,获得的结果对介观热电子器件的研制有一定的理论指导意义. 关键词： 热电子制冷机 摇摆棘齿 性能参数 传输矩阵法     

Questions concerning the generalized Hartman effect

With reference to a particle tunneling through two successive barriers, it seems to have been generally accepted that the tunneling time does not depend on the separation distance between the barriers. This phenomenon has been called the generalized Hartman effect. In this Letter, we point out a lack of mathematical rigor in the reasoning by which this effect was deduced about ten years ago. A mathematically rigorous treatment shows us that the tunneling time does indeed depend on the length of the free space between the barriers.     

InAs/InP柱型量子线中隧穿时间和逃逸问题的研究

在有效质量近似和绝热近似下,利用转移矩阵法研究了电子通过In As/In P/In As/In P/In As柱形量子线共振隧穿二极管的输运问题,分析和讨论了电子居留时间以及电子的逃逸过程.详细研究了外加电场、结构尺寸效应对居留时间和电子逃逸的影响.居留时间随电子纵向能量的演化呈现出共振现象;同时,结构的非对称性对电子居留时间有很大的影响,随着结构非对称性的增加,居留时间表现出不同的变化.利用有限差分方法研究了非对称耦合量子盘中电子的相干隧穿逃逸过程.     

Spin-dependent delay time and Hartman effect in asymmetrical graphene barrier under strain

We study the spin-dependent tunneling time, including group delay and dwell time, in a graphene based asymmetrical barrier with Rashba spin–orbit interaction in the presence of strain, sandwiched between two normal leads. We find that the spin-dependent tunneling time can be efficiently tuned by the barrier width, and the bias voltage. Moreover, for the zigzag direction strain although the oscillation period of the dwell time does not change, the oscillation amplitude increases by increasing the incident electron angle. It is found that for the armchair direction strain unlike the zigzag direction the group delay time at the normal incidence depends on the spin state of electrons and Hartman effect can be observed. In addition, for the armchair direction strain the spin polarization increases with increasing the RSOI strength and the bias voltage. The magnitude and sign of spin polarization can be manipulated by strain. In particular, by applying an external electric field the efficiency of the spin polarization is improved significantly in strained graphene, and a fully spin-polarized current is generated.     

Generation and classification of the translational shape-invariant potentials based on the analytical transfer matrix method

For the conventional translational shape-invariant potentials (TSIPs), it has demonstrated that the phase contribution devoted by the scattered subwaves in the analytical transfer matrix quantization condition is integrable and independent of n. Based on this fact we propose a novel strategy to generate the whole set of conventional TSIPs and classify them into three types. The generating functions are given explicitly and the Morse potential is taken as an example to illustrate this strategy.     

Generation and classification of the translational shape-invariant potentials based on the analytical transfer matrix method

For the conventional translational shape-invariant potentials (TSIPs), it has demonstrated that the phase contribution devoted by the scattered subwaves in the analytical transfer matrix quantization condition is integrable and independent of n. Based on this fact we propose a novel strategy to generate the whole set of conventional TSIPs and classify them into three types. The generating functions are given explicitly and the Morse potential is taken as an example to illustrate this strategy.     

A numerical method to calculate dwell time for electron in semiconductor nanostructure

To some extent,the operational quickness of semiconductor devices depends on the transmission time of an electron through semiconductor nanostructures.However,the calculation of transmission time is very difficult,thanks to both the contentious definition of the transmission time in quantum mechanics and the complicated effective potential functions experienced by electrons in semiconductor devices.Here,based on an improved transfer matrix method to numerically solve the Schr?dinger equation and...     

Exact solution to the curve crossing problems of two linear diabatic potentials by transfer matrix method

In the present work we have reported a simple exact analytical solution to the curve crossing problem of two linear diabatic potentials by transfer matrix method. Our problem assumes the crossing of two linear diabatic potentials which are coupled to each other by an arbitrary coupling (in contrast to linear potentials in the vicinity of crossing points) and for numerical calculation purposes this arbitrary coupling is taken as Gaussian coupling which is further expressed as a collection of Dirac delta functions. Further we calculated the transition probability from one diabatic potential to another by the use of this method.     

Quantum reflection as the reflection of subwaves

This paper studies quantum reflection with recent research on reflection coefficient. Based on the analytical transfer matrix method, a novel explanation for this phenomenon is proposed that quantum reflection is the reflection of subwaves, which originate inherently from the inhomogeneity of the fields and is always neglected in the semiclassical regime. Comparison with exact formula and the numerical calculations for different potentials has confirmed the reliability and the validity of the proposed theory.     

On particles tunneling from the Taub-NUT-AdS black hole

This paper discusses tunneling of scalar particles and Dirac particles from the Taub-NUT-AdS black hole by the Hamilton--Jacobi equation, initially used by Angheben et al, and the Dirac equation, recently proposed by Kerner and Mann. This is performed in the dragging coordinate frame so as to avoid the ergosphere dragging effect. A general form is obtained for the temperature of scalar and Dirac particles tunneling from the Taub-NUT-Ads black hole, which is commensurate with other methods as expected.     

对称抛物势阱磁性隧道结中的自旋输运及磁电阻效应

研究了两端具有铁磁接触的对称抛物势阱磁性隧道结(F/SPW/F)中自旋相关的隧穿概率和隧穿磁电阻,讨论了量子尺寸效应和Rashba 自旋轨道耦合作用对自旋极化输运特性的影响.研究结果表明:隧穿概率和隧穿磁电阻随抛物势阱宽度的增加发生周期性的振荡.抛物势阱深度的增加减小了隧穿概率和隧穿磁电阻的振荡频率.Rashba 自旋轨道耦合强度的增加加大了隧穿概率和隧穿磁电阻的振荡频率.隧穿概率和隧穿磁电阻的振幅和峰谷比强烈依赖于两铁磁电极中磁化方向的夹角. 关键词： 磁性隧道结 Rashba 自旋轨道耦合 隧穿概率 隧穿磁电阻     

介观LC电路中的量子隧道效应

考虑到电子在纳米电容器中的运动是一个单电子隧穿过程,因而将电容器作为一个隧道结,应用隧道模型的稳态法,研究了介观LC电路中的电流电压特性.结果表明:由于库仑力的作用,介观LC电路中存在着阈值电压.当外加电压小于阈值电压时,隧穿电流为零,显示出库仑阻塞现象;当外加电压远大于阈值电压时,隧穿电流与电压成正比. 关键词： 介观LC电路 库仑阻塞 单电子隧道过程     

A local view of the Kondo effect: Scanning tunneling spectroscopy

The fascinating many-body physics involved in the interaction of a single magnetic impurity with the conduction electrons of its nonmagnetic metallic host is reflected in unconventional phenomena in magnetism, transport properties and the specific heat. Characteristic low-energy excitations, termed the Kondo resonance, are generally believed to be responsible for this striking behaviour. However, in spite of an intense research for over more than 30 years, a direct spectroscopic observation of the Kondo resonance on individual magnetic adatoms withstood experimental efforts hitherto. The development of low-temperature scanning tunneling microscopes (STM) operating under ultrahigh vacuum (UHV) conditions has provided new opportunities for investigating locally the electronic structure at surfaces. At low temperatures, due to the reduced broadening of the Fermi level of the STM tip and the sample, rather high energy resolution (≤ 1 meV) in scanning tunneling spectroscopy (STS) is achievable. Moreover, the absence of diffusion together with the spatial resolution of the STM enables detailed studies of electronic states on and near single adsorbed atoms and other nanoscale structures. Recently, for the first time, two such STS/STM experiments spatially resolved the electronic properties of individual magnetic adatoms displaying the Kondo effect. In particular, the observed Fano lineshape of the Kondo resonance reveals unambiguously the details of the quantum mechanical interference between the localized orbital and the conduction electrons on an atomic length scale [1,2]. This achievement of the detection of individual magnetic atoms with atomic resolution opens new perspectives for probing magnetic nanostructures.     

Tunneling time and the post-tunneling position of an electron through a potential barrier in an anisotropic semiconductor

Tunneling time and post-tunneling position of an electron incident on a heterostructure grown on anisotropic materials are derived by solving an effective mass equation including off-diagonal effective mass tensor elements. The effects of different effective masses for a heterostructure junction are also included.     

Temperature-dependent theory of tunneling in the fractional quantum Hall effect

Recent experiments have studied the tunneling current between two edges of the same fractional quantum Hall liquid as a function of temperature and voltage. The experimental findings for low temperatures are at odds with the model where the edges are described as chiral Luttinger liquids, while the data at high temperatures are quite consistent with the same model. Here, we argue that a temperature dependence of the tunneling amplitude, not foreseen in previous works, can explain this discrepancy.