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1.
《Physics letters. A》1997,234(3):233-237
Within the parabolic conduction-band approach, a modified one-dimensional effective mass Schrödinger equation, including the magneto-coupling effect between the longitudinal motion component and the transverse Landau orbits of an electron, is strictly derived. This magneto-coupling effect is generated from the space-dependent effective mass of the electron. Numerical calculations for single barrier structures show that the magneto-coupling has a series of important effects on the transmission probability and the above-barrier quasi-bound states. We suggest that the magneto-coupling effect may be observed by measurements of the optical absorption spectrum in the single barrier structures. 相似文献
2.
In analogy with the definition of resonant or quasi-bound states used in three-dimensional quantal scattering, we define the
quasi-bound states that occur in one-dimensional transmission generated by twin symmetric potential barriers and evaluate
their energies and widths using two typical examples: (i) twin rectangular barrier and (ii) twin Gaussian-type barrier. The
energies at which reflectionless transmission occurs correspond to these states and the widths of the transmission peaks are
also the same as those of quasi-bound states. We compare the behaviour of the magnitude of wave functions of quasi-bound states
with those for bound states and with the above-barrier state wave function. We deduce a Breit-Wigner-type resonance formula
which neatly describes the variation of transmission coefficient as a function of energy at below-barrier energies. Similar
formula with additional empirical term explains approximately the peaks of transmission coefficients at above-barrier energies
as well. Further, we study the variation of tunnelling time as a function of energy and compare the same with transmission,
reflection time and Breit-Wigner delay time around a quasi-bound state energy. We also find that tunnelling time is of the
same order of magnitude as lifetime of the quasi-bound state, but somewhat larger. 相似文献
3.
Z. M. Wang M. Zhang Y. C. Li 《Physica E: Low-dimensional Systems and Nanostructures》2003,18(4):469-474
In this paper we study the tunneling transport phenomena in a step-barrier structure under the influence of a longitudinal magnetic field, where the magneto-coupling effect is taken into account between the longitudinal motion component and the transverse Landau orbits of an electron. We also present numerical results of single square-barrier and asymmetrical double-barrier heterostructures for comparison. The results show that the coupling effect can play important role during the electronic tunneling process. It not only causes a significant shift of resonant peaks toward the low-energy region, but also enhances the transmission probability. 相似文献
4.
Wave-packet time-dependent quantum mechanics is used to calculate the tunneling probability through a double-barrier ZnSe/ZnTe structure. The time-dependent transmission characteristics are obtained for several structures, and detailed electron dynamics is presented. The resonant peaks due to the presence of the discrete energy levels in the quantum well as well as in the barrier region are observed. 相似文献
5.
R.C AshooriH.B Chan 《Solid State Communications》2003,127(2):79-88
We have developed a technique capable of measuring the tunneling current into both localized and conducting states in a 2D electron system (2DES). The method yields I-V characteristics for tunneling with no distortions arising from low 2D in-plane conductivity. We have used the technique to determine the pseudogap energy spectrum for electron tunneling into and out of a 2D system and, further, we have demonstrated that such tunneling measurements reveal spin relaxation times within the 2DEG. Pseudogap: In a 2DEG in perpendicular magnetic field, a pseudogap develops in the tunneling density of states at the Fermi energy. We resolve a linear energy dependence of this pseudogap at low excitations. The slopes of this linear gap are strongly field dependent. No existing theory predicts the observed behavior. Spin relaxation: We explore the characteristics of equilibrium tunneling of electrons from a 3D electrode into a high mobility 2DES. For most 2D Landau level filling factors, we find that electrons tunnel with a single, well-defined tunneling rate. However, for spin-polarized quantum Hall states (ν=1, 3 and 1/3) tunneling occurs at two distinct rates that differ by up to two orders of magnitude. The dependence of the two rates on temperature and tunnel barrier thickness suggests that slow in-plane spin relaxation creates a bottleneck for tunneling of electrons. 相似文献
6.
The phonon-assisted resonant tunneling is studied for the double barrier structures in a longitudinal magnetic field. Using the scattering matrix approach with an appropriate one-particle Green's function we are able to calculate the current and the zero frequency shot noise power spectrum in a large range of the magnetic field and to any order of the electron-phonon interaction. Obtained results describe well the relevant experimental data and provide new suggestions for further examinations. 相似文献
7.
J.-J. Shi B.C. Sanders S.-H. Pan 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(1):113-119
We calculate the electron-phonon scattering rate for an asymmetric double barrier resonant tunneling structure based on dielectric
continuum theory, including all phonon modes, and show that interface phonons contribute much more to the scattering rate
than do bulk-like LO phonons for incident energies which are approximately within an order of magnitude of the Fermi energy.
The maximum scattering rate occurs for incident electron energies near the quantum well resonance. Subband nonparabolicity
has a significant influence on electron-phonon scattering in these structures. We show that the relaxation time is comparable
to the dwell time of electrons in the quantum well for a typical resonant tunneling structure.
Received: 23 December 1997 / Revised: 24 March 1998 / Accepted: 9 March 1998 相似文献
8.
在有效质量近似理论下,利用转移矩阵和有效垒高方法研究了有限磁场下含结构缺陷的多组分超晶格中局域电子态的性质.在考虑各组分层有效质量的失配时,外加磁场会导致磁耦合效应的出现.磁耦合效应不仅引起局域电子能级的量子化,并且随着朗道指数或磁场强弱的变化,局域能级及其局域程度都会发生显著移动,特别是对高能区域的局域电子态影响更大.此外,还计算了电子输运系数,讨论了含结构缺陷的三组分超晶格中局域电子能级与输运谱透射禁区中的共振透射峰的关系,发现两者之间有着很好的对应关系,为相应的实验研究提供了依据.
关键词:
超晶格
局域电子态
磁场 相似文献
9.
Recursion formulae for the reflection and the transmission probability amplitudes and the eigenvalue equation for multistep potential structures are derived. Using the recursion relations, a dispersion equation for periodic potential structures is presented. Some numerical results for the transmission probability of a double barrier structure with scattering centers, the lifetime of the quasi-bound state in a single quantum well with an applied field, and the miniband of a periodic potential structure are presented. 相似文献
10.
L.M. Schmitt 《Applied Physics A: Materials Science & Processing》1999,68(5):553-558
We discuss the transmission coefficient τd in non-repetitive, one-dimensional, rectangular double-barrier structures without simplifications such as strongly attenuating
barriers, strong localization, or overall constant effective tunneling mass of the electron. For resonance τd=1, we obtain two non-approximative conditions which require different resonance energies of the tunneling electron than previously
reported in the literature. In fact, the resonance peaks are shifted to higher energy levels in the order of the width of
the peaks due to the effect of non-constant tunneling mass. We investigate the dependence of the resonance condition and the
shape of the resonance peaks in regard to perturbation of the electron energy, the gap width as well as the barrier width
and height. Resonance is stable for variation of the barrier width but sensitive for variation of the barrier height and the
gap width.
Received: 9 December 1998 / Accepted: 5 January 1999 / Published online: 31 March 1999 相似文献
11.
Dynamics of the Dirac fermions, in particular the transmission coefficient and the resonant tunneling lifetime are studied across a bilayer graphene electrostatic double barrier structure modulated by an in plane homogeneous electric field. Asymmetric Fano type resonances are noted for the first time in the transmission spectrum of the bilayer graphene nanostructures and are found to be highly sensitive to the direction of incidence of the charge carriers and the applied homogeneous electric field. The effect of the external field on the extended and the evanescent modes is also analysed. Resonant tunneling lifetime is found to be highly anisotropic in nature. The chiral carriers are either accelerated or decelerated by the electric field depending on the energy of the quasi-bound states, the angle of incidence and the magnitude of the applied field. Effects of the external field on the localization of the chiral carriers are also discussed. 相似文献
12.
G. Göppert H. Grabert 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(4):687-704
We study the linear conductance of single electron devices showing Coulomb blockade phenomena. Our approach is based on a
formally exact path integral representation describing electron tunneling nonperturbatively. The electromagnetic environment
of the device is treated in terms of the Caldeira-Leggett model. We obtain the linear conductance from the Kubo formula leading
to a formally exact expression which is evaluated in the semiclassical limit. Specifically we consider three models. First,
the influence of an electromagnetic environment of arbitrary impedance on a single tunnel junction is studied focusing on
the limits of large tunneling conductance and high to moderately low temperatures. The predictions are compared with recent
experimental data. Second, the conductance of an array of N tunnel junctions is determined in dependence on the length N of the array and the environmental impedance. Finally, we consider a single electron transistor and compare our results for
large tunneling conductance with experimental findings.
Received 2 February 2000 相似文献
13.
A. John Peter 《Physics letters. A》2008,372(31):5239-5242
The spin dependent electron transmission through a non-magnetic III-V semiconductor symmetric well is studied theoretically so as to investigate the output transmission current polarization at zero magnetic field. Transparency of electron transmission is calculated as a function of electron energy as well as the well width, within the one electron band approximation along with the spin-orbit interaction. Enhanced spin-polarized resonant tunneling in the heterostructure due to Dresselhaus and Rashba spin-orbit coupling induced splitting of the resonant level is observed. We predict that a spin-polarized current spontaneously emerges in this heterostructure. This effect could be employed in the fabrication of spin filters, spin injectors and detectors based on non-magnetic semiconductors. 相似文献
14.
N. Vandewalle M. Ausloos 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):257-261
The resonance splitting in finite semiconductor superlattices which consist of a number of electric barriers is investigated.
It is found that (n-1)-fold splitting for n-barrier tunneling obtained in periodic superlattices of identical barriers no longer holds for superlattices which are periodically
juxtaposed with two different building barriers. In general, one resonant domain in the former splits into two resonant subdomains
in the latter, and splitting occurs each time when two new barriers are added. The results indicate that the resonance splitting
is determined not only by the structure but also by the parameters of building blocks.
Received: 12 October 1997/ Revised and Accepted: 5 January 1998 相似文献
15.
电子横向运动对共振隧穿的影响 总被引:2,自引:0,他引:2
讨论了电子横纵方向运动耦合时的隧穿现象,对CdSe/Zn1-xCdxSe方形双势垒结构和抛物形双势垒结构的数值计算表明,在零偏压和非零偏压情况下,电子横向运动对共振隧穿的影响是不容忽略的。 相似文献
16.
The quantum conductance for electrons scattering from a uniform scatterer in a narrow-wire semiconductor is calculated. Instead of getting the conductance directly from the calculation of transmission coefficient, we calculate the reflection coefficient instead. The transmission coefficient is then calculated by using the conservation law, T=I−R. This alternative method can avoid the instability of the conductance obtained by including more evanescent modes for a finite-range scatterer in a narrow-wire semiconductor. This method is applied to a semi-infinite strip potential barrier and a rectangular potential barrier in a narrow wire. The quantum stepwise conductance is obtained in both cases. For a repulsive rectangular potential barrier, there are oscillations in each stepwise conductance. For an attractive rectangular potential barrier, there exist multiple quasi-bound states below the sub-band energies which can cause the drop of the quantum conductance. The effect of the continuum quasi-bound states diminishes as the energy of the incident electron increases, but the influence of the discrete quasi-bound states still persists. 相似文献
17.
Transmission resonances in magnetic-barrier structures 总被引:1,自引:0,他引:1
Y. Guo Z.-Q. Li B.-L. Gu Q. Sun J.-Z. Yu Y. Kawazoe 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):263-270
Quantum transport properties of electrons in simple magnetic-barrier (MB) structures and in finite MB superlattices are investigated
in detail. It is shown that there exists a transition of transmission resonances, i.e., from incomplete transmission resonances in simple MB structures consisting of unidentical blocks, to complete transmission
resonances in comparatively complex MB structures (, n is the number of barriers). In simple unidentical block arrangements in double- and triple-MB structures we can also obtain
complete transmission by properly adjusting parameters of the building blocks according to ky-value (ky is the wave vector in y direction). Strong suppression of the transmission and of the conductance is found in MB superlattices which are periodic
arrangements of two different blocks. The resonance splitting effect in finite MB superlattices is examined. It is confirmed
that the rule (i.e., for n-barrier tunneling the splitting would be (n-1)-fold) obtained in periodic electric superlattices can be extended to periodically arranged MB superlattices of identical
blocks through which electrons with tunnel, and it is no longer proper for electrons with k
y
<0 to tunnel.
Received: 18 August 1997 / Revised: 20 September 1997 / Accepted: 13 October 1997 相似文献
18.
H.-K. Zhao J. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(3):513-524
The time-dependent transport through an ultrasmall quantum dot coupling to two electron reservoirs is investigated. The quantum
dot is perturbed by a quantum microwave field (QMF) through gate. The tunneling current formulae are obtained by taking expectation
values over coherent state (CS), and SU(1,1) CS. We derive the transport formulae at low temperature by employing the nonequilibrium
Green function technique. The currents exhibit coherent behaviors which are strongly associated with the applied QMF. The
time-dependent currents appear compound effects of resonant tunneling and time-oscillating evolution. The time-averaged current
and differential conductance are calculated, which manifest photon-assisted behaviors. Numerical calculations reveal the similar
properties as those in classical microwave field (CMF) perturbed system for the situations concerning CS and squeezed vacuum
SU(1,1) CS. But for other squeezed SU(1,1) CS, the tunneling behavior is quite different from the system perturbed by a single
CMF through gate. Due to the quantum signal perturbation, the measurable quantities fluctuate fiercely.
Received 28 May 1998 相似文献
19.
20.
G.-Y. Sun C.-X. Wu Y. Chen Z.-L. Yang 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(4):459-464
Using the Keldysh nonequilibrium Green function method, we
theoretically investigate the electron transport properties of a
quantum dot coupled to two ferromagnetic electrodes, with
inelastic electron-phonon interaction and spin flip scattering
present in the quantum dot. It is found that the electron-phonon
interaction reduces the current, induces new satellite polaronic
peaks in the differential conductance spectrum, and at the same
time leads to oscillatory tunneling magnetoresistance effect. Spin
flip scattering suppresses the zero-bias conductance peak and
splits it into two, with different behaviors for parallel and
anti-parallel magnetic configuration of the two electrodes.
Consequently, a negative tunneling magnetoresistance effect may
occur in the resonant tunneling region, with increasing spin flip
scattering rate. 相似文献