共查询到20条相似文献,搜索用时 15 毫秒
1.
Y. Guo B. Wang B.-L. Gu Y. Kawazoe 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(4):509-513
We investigate characteristics of spin tunneling time in ZnSe/Ze1-xMnxSe multilayers under the influence of both an electric field and a magnetic field. The results indicate that the tunneling
time shows complicated oscillations and significant spin separation for electrons with different spin orientations traversing
semimagnetic semiconductor heterostructures. It is also shown that the tunneling time exhibits obvious asymmetry in opposite
tunneling directions for electrons tunneling through asymmetric heterostructures, which mainly occurs in resonant regions.
The degree of the asymmetry of the tunneling time is not only spin-polarization dependent but also external-field induced.
Received 10 July 2001 相似文献
2.
Maowang Lu Lide Zhang Yunxia Jin Xiaohong Yan 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(4):565-570
We study the spin-dependent transport properties of the nanostructures consisting of realistic magnetic barriers produced
by the deposition of ferromagnetic stripes on heterostructures. It is shown that, only in the nanostructures with symmetric
magnetic field with respect to the magnetic-modulation direction, electrons exhibit a considerable spin-polarization. It is
also shown that the degree of the electron spin polarization is greatly dependent on the ferromagnetic stripe and its position
relative to the 2DEG. A much larger electron-spin polarization can be obtained by properly fabricating the ferromagnetic stripe
and by adjusting its distance above the 2DEG.
Received 27 December 2001 and Received in final form 13 March 2002 Published online 25 June 2002 相似文献
3.
P. Schwab R. Raimondi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):5-8
We consider non-equilibrium transport in disordered conductors. We calculate the interaction correction to the current for
a short wire connected to electron reservoirs by resistive interfaces. In the absence of charging effects we find a universal
current-voltage-characteristics. The relevance of our calculation for existing experiments is discussed as well as the connection
with alternative theoretical approaches.
Received 2 September 2002 Published online 29 October 2002 相似文献
4.
Z. H. Dai J. Ni Y. M. Sun W. T. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(4):439-446
We investigate the time-dependent dynamical behavior of electron transport
in AlGaAs/GaAs double-barrier structures under a high-frequency radiation
field. The effects of the radiation field with different amplitude and
frequency on the real-time and mean current-voltage curves are taken into
account. We find that the amplitude and frequency of the radiation field
affect the final stable state current-voltage (I-V) behaviors, which leads
to the switching between different current states at a smaller bias than
that of the absence of the radiation field, and both current hysteresis and
resonant peaks are suppressed by the external radiation field. The high
radiation field strength can make the resonant peak of current split and the
hysteresis of current disappear. This effect provides the potential to use
double-barrier structure as a THz photoelectric switch. 相似文献
5.
N. Fujima 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):185-188
The non-collinearity of magnetic moments of pentagonal bipyramid Cr7, Mn7 and Fe7 clusters is discussed. The magnetic moments are calculated by the discrete variational non-collinear spin-density functional
method. For the Cr7 cluster, a coplanar magnetic arrangement appears at the large interatomic distance. With decreasing the interatomic distance,
the coplanar arrangement changes to the parallel arrangement with a small absolute magnetic moment. For the Mn7 cluster, the magnetic arrangement changes from coplanar to antiparallel with decreasing the interatomic distance. Also for
the Fe7 cluster, some coplanar magnetic moments appear at the interatomic distance of 2.23 ?. In these coplanar magnetic arrangements,
the magnetic moment at the basal site of the pentagon rotates with a step of 144 degrees for the Cr7 clusters and 72 degrees for the Mn7 and Fe7 clusters.
Received 30 November 2000 相似文献
6.
S. Anantha Ramakrishna N. Kumar 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(4):515-519
We re-examine and correct an earlier derivation of the distribution of the Wigner phase delay time for wave reflection from
a long one-dimensional disordered conductor treated in the continuum limit. We then numerically compare the distributions
of the Wigner phase delay time and the dwell time, the latter being obtained by the use of an infinitesimal imaginary potential
as a clock, and investigate the effects of strong disorder and a periodic (discrete) lattice background. We find that the
two distributions coincide even for strong disorder, but only for energies well away from the band-edges.
Received 11 June 2001 and Received in final form 30 July 2001 相似文献
7.
Using the transfer matrix method, the transmission probability, the spin polarization and the electron conductance of a ballistic electron are studied in detail in a nanostructure. We observe that these quantities sensitively depend on the number of periodic magnetic-electric barriers. As the number of periods increases, the resonance splitting increases, the number of the resonance peaks increases and the peaks become sharper as well as the spin polarization being enhanced. Surprisingly, a polarization of nearly 100% can be achieved by spin-dependent resonant tunneling in this structure, although the average magnetic field of the structure is zero. 相似文献
8.
Zhenhong Dai Jinzuo Sun Lide Zhang Maowang Lu Zuohong Li Shiyong Huang 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):141-145
Artificial molecules, namely laterally coupled quantum dots with a three-dimensional spherical confinement potential well
of radius R and depth V
0, were studied by the unrestricted Hartree-Fock-Roothaan (UHFR) method. By varying the distance d between the centers of the two coupled quantum dots, the transition from the strong coupling situation to the weak one is
realized. Hund's rule, suitable for a single quantum dot is destroyed in certain conditions in the artificial molecule. For
example, in the few-electron system of the strongly coupled quantum-dot molecule, a transformation of spin configuration has
been found.
Received 8 March 2002 / Received in final form 29 May 2002 Published online 17 September 2002 相似文献
9.
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
10.
F. Zhai Y. Guo B.-L. Gu 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(3):405-411
By use of the scattering matrix method, we investigate the coupling effects of layers on spin-polarized transport through
semimagnetic semiconductor heterostructures with triple paramagnetic layers. Due to the coupling between double non-magnetic
layers or among triple paramagnetic layers, spin tunneling exhibits interesting and complex features, which are determined
by the structural configuration, the external fields as well as the spin orientations. It is shown that for electrons with
either spin orientation tunneling through the symmetric or asymmetric heterostructures with triple paramagnetic layers, transmission
resonances can approach the optimum under several biases. Moreover, for asymmetric structures, the resonant enhancement can
occur under both several positive and negative biases. The spin-dependent resonant enhancement is also clearly reflected in
the current density. In addition, for spin electrons traversing the multilayer heterostructure, the resonant splitting occurs
in the transmission, which shows rich variations with the bias. These interesting results may be helpful to the development
of spintronic devices.
Received 28 April 2001 相似文献
11.
M. Giroud K. Hasselbach H. Courtois D. Mailly B. Pannetier 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):103-109
We present electrical transport experiments performed on submicron hybrid devices made of a ferromagnetic conductor (Co) and
a superconducting (Al) electrode. The sample was patterned in order to separate the contributions of the Co conductor and
of the Co-Al interface. We observed a strong influence of the Al electrode superconductivity on the resistance of the Co conductor.
This effect is large only when the interface is highly transparent. We characterized the dependence of the observed resistance
decrease on temperature, bias current and magnetic field. As the differential resistance of the ferromagnet exhibits a non-trivial
asymmetry, we claim that the magnetic domain structure plays an important role in the electron transport properties of superconducting
/ ferromagnetic conductors.
Received 9 July 2002 / Received in final form 22 October 2002 Published online 27 January 2003
RID="a"
ID="a"e-mail: herve.courtois@grenoble.cnrs.fr
RID="b"
ID="b"associated to Université Joseph Fourier 相似文献
12.
Mao-Wang Lu 《Solid State Communications》2005,134(10):683-688
We report on a theoretical study of spin-dependent electron transport in a two-dimensional electron gas (2DEG) modulated by a stripe of ferromagnetic metal under an applied voltage. A general formula of transmission probability for electronic tunneling through this system is obtained. Based on this formula, it is shown that large spin-polarized current can be achieved in such a device. It is also shown that the degree of electron-spin polarization is strongly dependent upon the applied voltage to the stripe in the device. These interesting properties may provide an alternative scheme to spin-polarize electrons into semiconductors, and this device may be used as a voltage-tunable spin-filter. 相似文献
13.
A. A. Shokri 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(3):475-481
Theoretical studies on spin-dependent transport in magnetic tunnel
heterostructures consisting of two diluted magnetic semiconductors
(DMS) separated by a nonmagnetic semiconductor (NMS) barrier, are
carried in the limit of coherent regime by including the effect of
angular dependence of the magnetizations in DMS. Based on
parabolic valence band effective mass approximation and
spontaneous magnetization of DMS electrodes, we obtain an
analytical expression of angular dependence of transmission for
DMS/NMS/DMS junctions. We also examine the dependence of spin
polarization and tunneling magnetoresistance (TMR) on barrier
thickness, temperature, applied voltage and the relative angle
between the magnetizations of two DMS layers in GaMnAs/GaAs/GaMnAs
heterostructures. We discuss the theoretical interpretation of
this variation. Our results show that TMR of more than 65% are
obtained at zero temperature, when one GaAs monolayer is used as a
tunnel barrier. It is also shown that the TMR decreases rapidly
with increasing barrier width and applied voltage; however at high
voltages and low thicknesses, the TMR first increases and then
decreases. Our calculations explain the main features of the
recent experimental observations and the application of the
predicted results may prove useful in designing nano spin-valve
devices. 相似文献
14.
The behavior of Wigner phase delay time in the reflection mode is studied taking into account the real band structure of Kane type semiconductor quantum ring. It's calculated the analytical expression for the saturated delay time. It's shown that the saturated delay time is independent of the width of the opaque barrier. 相似文献
15.
Current-voltage (J-V) and differential-conductivity-voltage ( dJ/dV-V) characteristics are analytically calculated at zero temperature for a point contact consisting of: two Peierls conductors
P
( = 1, 2) separated by an insulator (I). Here P is a conductor with charge density wave (CDW). The J-V and dJ/dV-V characteristics depend on the CDW phases ( = 1, 2) in the mean field approximation. To calculate them analytically we assumed, = ≡Δ where ( = 1, 2) are the energy gaps of P
( = 1, 2). The current J has a discontinuous jump at eV = 2Δ for ϕ
1 = ϕ
2≠ 0. The differential conductivity dJ/dV has a singularity at eV = 2Δ for ϕ
1 = ϕ
2≠ 0. The relation J(V,ϕ
1,ϕ
2) = - J(- V,ϕ
1 + π,ϕ
2 + π) is obtained.
Received 4 July 2001 and Received in final form 13 September 2001 相似文献
16.
Yong-Hong Kong Mao-Wang Lu Wei-Hua Tang Gui-Lian Zhang 《Solid State Communications》2007,142(3):143-147
We theoretically investigate the giant magnetoresistance (GMR) effect in general magnetically modulated semiconductor nanosystems, which can be realized experimentally by depositing two parallel ferromagnetic strips on the top of a heterostructure. Here the exact magnetic profiles and arbitrary magnetization direction of ferromagnetic strips are emphasized. It is shown that a considerable GMR effect can be achieved in such nanosystems due to the significant transmission difference for electrons tunneling through parallel and antiparallel magnetization configurations. It is also shown that the magnetoresistance ratio is strongly influenced by the magnetization direction of ferromagnetic strips in nanosystems, thus possibly leading to tunable GMR devices. 相似文献
17.
Mao-Wang Lu 《Solid State Communications》2007,141(5):248-251
We propose a Magnetoresistance device in a magnetically modulated two-dimensional electron gas, which can be realized experimentally by the deposition of two parallel ferromagnetic strips on the top and bottom of a semiconductor heterostructure. It is shown that there exists a significant transmission difference for electrons through the parallel and antiparallel magnetization configurations of such a device, which leads to a considerable magnetoresistance effect. It is also shown that the magnetoresistance ratio of the device depends greatly on the magnetic strength difference in the two delta barriers of the system. 相似文献
18.
We report on a theoretical investigation of the giant magnetoresistance (GMR) effect in hybrid ferromagnetic-Schottky-metal and semiconductor nanosystem. Experimentally, this GMR device can be realized by the deposition of two ferromagnetic (FM) stripes and one Schottky normal metal (NM) in parallel way on the top of a semiconductor GaAs heterostructure. The GMR effect emanates from the significant transmission difference for electrons tunneling through parallel and antiparallel magnetization configurations of the device, and its magnetoresistance ratio (MR) can reach the order of 106%. Furthermore, it is also shown that the MR of the device depends strongly on the relative location of the Schottky NM stripe between two FM stripes. 相似文献
19.
Ben-Yuan Gu Yao Lu Tzong-Jer Yang 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):493-502
We present numerical investigations of the transmission properties of electrons in a normal quantum wire tangentially attached
to a superconductor ring threaded by magnetic flux. A point scatterer with a δ -function potential is placed at node to model
scattering effect. We find that the transmission characteristics of electrons in this structure strongly depend on the normal
or superconducting state of the ring. The transmission probability as a function of the energy of incident electrons, in the
case of a superconductor ring threaded by one quantum magnetic flux, emerges one deep dip, imposed upon the first broad bump
in spectrum. This intrinsic conductance dip originates from the superconductor state of the ring. When increasing the magnetic
flux from one quantum magnetic flux to two, the spectrum shifts toward higher energy region in the whole. This conductance
dip accordingly shifts and appears in the second bump. In the presence of a point-scatterer at the node, the spectrum is substantially
modified. Based on the condition of the formation of the standing wave functions in the ring and the broken of the time-reserve
symmetry of Schr?dinger equation after switching magnetic flux, the characteristics of transmission of electrons in this structure
can be well understood.
Received 6 November 2001 相似文献
20.
A. Sacchetti 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(2):229-232
Here we consider the dynamics of a two-level system under an external time-dependent field. We show that in the case of a
bichromatic field the dynamical localization effect is strongly sensitive with respect to the commensurability of the driving
frequencies.
Received 8 May 2002 / Received in final form 4 July 2002 Published online 24 September 2002
RID="a"
ID="a"e-mail: Sacchetti@unimo.it 相似文献