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1.
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
2.
Z.Y. Zeng Y. Xiang L.D. Zhang 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):699-705
We proposed a new kind of coupled coaxial cylindrical quantum wires structure - quantum cable, and calculated its single-electron
energy subband spectrum for the varying structure parameters, in order to investigate its subband motion in the structure
parameter space. It is shown that quantum cable has unique subband spectrum, which differs either from the (solid and hollow)
cylindrical quantum wire or from the usual coupled double quantum wires (CDQWs) structure. Aside from the two-fold degeneracy
induced by the cylindrical symmetry, crossings (accidental degeneracies) and anticrossings (repulsions) of quantum cable subbands
with different azimuthal and radial quantum numbers are observed as one of the cable structure parameters varies. This introduces
the dependence of the subband ladder on the structure parameters of the quantum cable structure. However, the subband with
the lowest azimuthal and radial quantum numbers remains the lowest subband and never crosses with the other subbands irrespective
of the value of structure parameters. As the coupling barrier is broadening (coupling becoming weak), some subbands bundling
toward another subband is seen before the extreme isolating limit achieved. Moreover, the separation between neighboring subbands
exhibits non-monotonous evolution as one changes the thickness of one of the cylindrical quantum wires, with a minimum existing
in the separation between some two adjacent subbands. Interesting optical and transport phenomena arising from these unique
subband properties of the quantum cable structure are also predicted.
Received 22 March 2000 and Received in final form 6 June 2000 相似文献
3.
F. Ernult L. Giacomoni A. Marty B. Dieny A. Vedyayev N. Ryzhanova 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(2):177-189
Discontinuous magnetic metal/insulator multilayers are formed of equally spaced layers of magnetic particles embedded in an
insulating matrix. Their electronic transport properties result from spin-polarized electron tunneling and Coulomb blockade
effect. The current-in-plane (CIP) and current-perpendicular-to plane (CPP) resistances change by several orders of magnitude
when the thicknesses of the metallic or insulating layers are varied. Calculations of the shape of the current lines in these
multilayers are presented. It is shown that pure CIP or CPP transport occur in these systems only when the CIP or CPP resistances
are very different in magnitude. If the two resistances are of the same order of magnitude, then the measured transport properties
in both geometries are a combination of CIP and CPP transport.
Received 9 October 2001 相似文献
4.
M. Glück A.R. Kolovsky H.J. Korsch N. Moiseyev 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(3):239-246
The paper discusses the metastable states of a quantum particle in a periodic potential under a constant force (the model
of a crystal electron in a homogeneous electric field), which are known as the Wannier-Stark ladder of resonances. An efficient
procedure to find the positions and widths of resonances is suggested and illustrated by numerical calculations for a cosine
potential, which are in excellent agreement with complex scaling resonance energies.
Received: 27 April 1998 / Revised: 21 July 1998 / Accepted: 3 August 1998 相似文献
5.
R. Baltin Y. Gefen G. Hackenbroich H.A. Weidenmüller 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(1):119-129
We investigate the Coulomb blockade resonances and the phase of the transmission amplitude of a deformed ballistic quantum
dot weakly coupled to leads. We show that preferred single-particle levels exist which stay close to the Fermi energy for
a wide range of values of the gate voltage. These states give rise to sequences of Coulomb blockade resonances with correlated
peak heights and transmission phases. The correlation of the peak heights becomes stronger with increasing temperature. The
phase of the transmission amplitude shows lapses by between the resonances. Implications for recent experiments on ballistic quantum dots are discussed.
Received 17 July 1998 相似文献
6.
A. Hilger N. Cüppers M. Tenfelde U. Kreibig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(1):115-118
We present novel experimental results about influences of surrounding foreign materials on optical properties of small silver
clusters. First we show spectra of free cluster beams produced with different seeding gases Ar, Kr, Xe. Second, we estimate, from measured spectra, the cluster deformations
and contact areas after deposition on different substrates (Cr2O3 and MgF2) at room temperature and on SiO2 at 110 K and between 160 K and 300 K. Third, we present and compare the static and dynamic charge transfer after embedding the clusters in various fluorides and compare with previous results on oxides.
Received 2 September 1998 and Received in final form 3 January 1999 相似文献
7.
C. Pennetta L.B. Kiss Z. Gingl L. Reggiani 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(1):61-65
We discuss a new type of excess noise strongly sensitive to non-homogeneous Joule heating of random resistor network and associated
with local sources of thermal noise. The evolution of the network towards an electrical breakdown of conductor-insulator type
is then studied by using a biased percolation model and it is analysed in terms of an excess-noise temperature. Monte Carlo
simulation results show a significant increase of the excess-noise temperature over the average temperature of the network.
Remarkably the excess-noise temperature scales with the resistance with an exponent of about 3. The predictivity of the model
can be tested on thin film resistors where the determination of the excess noise temperature should provide a valuable indicator
of the defectiveness of the film.
Received 13 April 1999 and Received in final form 7 May 1999 相似文献
8.
B. Duan X. -Y. Gu Z. -Q. Ma 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(1):9-12
The energies of some excited states with the total angular momentum L=0, 1 and 2. the total spin of two electrons S=0 and 1, and the even and odd parities are precisely calculated directly from the Schrödinger equation where the mass of the helium nucleus is finite. Moreover, we find that the solutions to the equation for the excited states have some more nodes, which can be used to distinguish the states with the same spectral term. 相似文献
9.
U. Kuhl E. Persson M. Barth H.-J. Stöckmann 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(2):253-259
A set-up is described allowing the automatic registration of wavefunctions of quasi-two-dimensional microwave billiards of
arbitrary shape. Tests of the apparatus with rectangular shaped billiards showed that a precision of some percent in the wavefunction
amplitudes can be obtained, as far as isolated resonances are considered. For the case of overlapping resonances, however,
the measurement yields wavefunctions which are close to a symmetric and an antisymmetric linear combination of the original
rectangle eigenfunctions. The cause for this at first sight surprising result is discussed.
Received 21 January 2000 相似文献
10.
O. Mustafa M. Odeh 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):143-148
A new pseudoperturbative (artificial in nature) methodical proposal [#!ref15!#] is used to solve for Schr?dinger equation
with a class of phenomenologically useful and methodically challenging anharmonic oscillator potentials . The effect of the [#!ref4!#,#!ref5!#] Padé approximant on the leading eigenenergy term is studied. Comparison with results
from numerical (exact) and several eligible (approximation) methods is made.
Received 2 July 1999 and Received in final form 18 November 1999 相似文献
11.
12.
H. Kellay J. Rouch 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(1):121-129
In this paper we study the influence of the magneto-coupling effect between the longitudinal motion component and the transverse
Landau orbits of an electron on transmission features in single barrier structures. Within the parabolic conduction-band approach,
a modified one-dimensional effective-mass Schr?dinger equation, including the magneto-coupling effect generated from the position-dependent
effective mass of the electron, is strictly derived. Numerical calculations for single barrier structures show that the magneto-coupling
effect brings about a series of the important changes for the transmission probability, the above-barrier quasi-bound states,
and the tunneling time. Through examining the variation of the above-barrier resonant-transmission spectrum with the barrier
width and observing the well-defined Lorentzian line-shape of the above-barrier resonant peaks, we convincingly show that
the above-barrier resonant transmission in single barrier structures is delivered by the above-barrier quasibound states in
the barrier region, just as the below-barrier resonant tunneling in double barrier structures is mediated by the below-barrier
quasi-bound states in the well. Furthermore, we come to the conclusion that the magneto-coupling effect brings about not only
the splitting of the above-barrier quasi-bound levels but also the striking reduction of the level-width of the quasi-bound
states, correspondingly, the substantial increase of the density of the quasi-bound states. We suggest that magneto-coupling
effects may be observed by the measurements of the optical absorption spectrum associated with the above-barrier quasi-bound
states in the single barrier structures.
Received: 26 September 1997 / Revised: 26 November 1997 / Accepted: 15 December 1997 相似文献
13.
14.
A. Brataas Yu.V. Nazarov J. Inoue G.E.W. Bauer 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(3):421-430
We study transport in ferromagnetic single-electron transistors. The non-equilibrium spin accumulation on the island caused
by a finite current through the system is described by a generalized theory of the Coulomb blockade. It enhances the tunnel
magnetoresistance and has a drastic effect on the time-dependent transport properties. A transient decay of the spin accumulation
may reverse the electric current on time scales of the order of the spin-flip relaxation time. This can be used as an experimental
signature of the non-equilibrium spin accumulation.
Received 6 May 1998 相似文献
15.
16.
L. Sheng H.Y. Teng D.Y. Xing 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(2):209-213
Using the two-point conductivity formula, we numerically evaluate the giant magnetoresistance (GMR) in magnetic superlattices
with currents in the plane of the layers (CIP), from which the effect of the interfacial roughness and magnetization configuration
on the GMR is studied. With increasing interfacial roughness, the maximal GMR ratio is found to first increase and then decrease,
exhibiting a peak at an optimum strength of interfacial roughness. For systems composed of relatively thick layers, the GMR
is approximately proportional to ,where is the angle between the magnetizations in two successive ferromagnetic layers, but noticeable departures from this dependence
are found when the layers become sufficiently thin.
Received 21 September 1998 and Received in final form 22 December 1998 相似文献
17.
M. I. Jaghoub 《The European Physical Journal A - Hadrons and Nuclei》2006,28(2):253-257
This work explores the application of perturbation formalism, developed for isotropic velocity-dependent potentials, to three-dimensional
Schr?dinger equations obtained using different orderings of the Hamiltonian. It is found that the formalism is applicable
to Schr?dinger equations corresponding to three possible ordering ambiguities. The validity of the derived expressions is
verified by considering examples admitting exact solutions. The perturbative results agree quite well with the exactly obtained
ones. 相似文献
18.
M. Monnerville J.M. Robbe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(3):381-387
The optical potential discrete variable representation method (OP-DVR) has been applied recently to calculate resonances in
the framework of the diabatic representation [J. Chem. Phys. 101, 7580 (1994)]. This method is based on the conjoint use of the discrete variable representation (DVR) method and the properties
of a complex absorbing potential (CAP). The OP-DVR method is the DVR version of the CAP stabilization method initially proposed
by Jolicard and Austin [Chem. Phys. Lett. 121, 106 (1985)]. In the present study, we show that this efficient and accurate method can also be applied within the adiabatic
representation since it allows one to overcome in a simple way, numerical difficulties associated with the first derivative
operator which appears in the expression of non adiabatic couplings. Within the OP-DVR method, the choice of the representation
(diabatic or adiabatic) is governed by physical arguments and by the fact that the potentials and the couplings are known
in one or the other of these two representations. In the case where the potentials and the couplings are obtained in the adiabatic
representation, we show in this paper that the transformation into the diabatic framework is not necessary. We demonstrate
that the discrete variable representation can be a simple and an efficient way to deal with the adiabatic representation.
Received: 30 April 1998 / Revised: 29 September 1998 /Accepted: 21 October 1998 相似文献
19.
S.-H. Dong 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(2):159-165
In terms of the modified Sturm-Liouville theorem, the Levinson theorem for the one-dimensional Klein-Gordon equation with
a symmetric potential V(x) is established. It is shown that the number N+ (N-) of bound states with even (odd) parity is related to the phase shift of the scattering states with the same parity at zero momentum as and The solution of the one-dimensional Klein-Gordon equation with the energy M or -M is called as a half bound state if it is finite but does not decay fast enough at infinity to be square integrable.
Received 22 December 1999 相似文献
20.
The Bethe-Salpeter (BS) equation in Minkowski space for scalar particles is solved for a kernel given by a sum of ladder and
cross-ladder exchanges. The solution of corresponding light-front (LF) equation, where we add the time-ordered stretched boxes,
is also obtained. Cross-ladder contributions are found to be very large and attractive, whereas the influence of stretched
boxes is negligible. Both approaches --BS and LF-- give very close results. 相似文献