共查询到20条相似文献,搜索用时 390 毫秒
1.
Based on the Floquet theory and Keldysh's nonequilibrium Green's function methods, we study the electron transport through the HgTe/CdTe quantum wells (QWs) irradiated by a monochromatic laser field. We find that when the laser field is applied, the edge states are split into a series of sidebands. When the Fermi level lies among these sidebands, the quantized plateau of the conductance is destroyed. Instead, the conductance versus the radiation frequency exhibits the successive oscillation peaks corresponding to the resonant tunneling through the sidebands of the edge states. The resonant interaction between the quasiparticles and the radiation field opens the gaps in the crossing region of the sidebands, which can be tuned by the radiation strength and frequency. This leads to the shift of the oscillation peaks in the conductance. We also show that the amplitudes of the oscillation peaks in the conductance are governed by the radiation strength and frequency. 相似文献
2.
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
3.
考虑自旋场效应晶体管中Rashba自旋轨道相互作用和自旋输运量子相干性,研究了势垒强度对自旋场效应晶体管的自旋相关量子输运的影响. 研究发现,势垒强度较低时,隧道结电导随Rashba自旋轨道相互作用强度的变化呈现明显的振荡现象,势垒强度较高时,电导表现出明显的势垒相关“电导开关”现象. 当势垒强度逐渐增强时,平行结构电导呈现出单调下降趋势,而反平行结构电导产生波动,这种波动导致该隧道磁阻也随势垒强度的变化表现出振荡现象,且在合适的准一维电子气厚度情况下隧道磁阻值可以产生正负反转,这个效应将会在基于自旋的电子器件信息的存储上获得应用.
关键词:
自旋场效应管
开关效应
量子相干
隧道磁阻 相似文献
4.
He Gao 《Physics letters. A》2008,372(35):5695-5700
We have investigated the mesoscopic transport properties of a quantum dot embedded Aharonov-Bohm (AB) interferometer applied with a rotating magnetic field. The spin-flip effect is induced by the rotating magnetic field, and the tunneling current is sensitive to the spin-flip effect. The spin-flipped electrons tunneling from the direct channel and the resonant channel interfere with each other to form spin-polarized tunneling current components. The non-resonant tunneling (direct transmission) strength and the AB phase φ play important roles. When the non-resonant tunneling (background transmission) exists, the spin and charge currents form asymmetric peaks and valleys, which exhibit Fano-type line shapes by varying the source-drain bias voltage, or gate voltage. The AB oscillations of the spin and charge currents exhibit distinct dependence on the magnetic flux and direct tunneling strength. 相似文献
5.
We theoretically investigate the effects of strain-induced pseudomagnetic fields on the transmission probability and the ballistic conductance for Dirac fermion transport in suspended graphene. We show that resonant tunneling through double magnetic barriers can be tuned by strain in the suspended region. The valley-resolved transmission peaks are apparently distinguishable owing to the sharpness of the resonant tunneling. With the specific strain, the resonant tunneling is completely suppressed for Dirac fermions occupying the one valley, but the resonant tunneling exists for the other valley. The valley-filtering effect is expected to be measurable by strain engineering. The proposed system can be used to fabricate a graphene valley filter with the large valley polarization almost 100%. 相似文献
6.
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
7.
Resonant transmission and Goos–Hänchen (GH) shift for Dirac fermion beams tunneling through graphene double velocity barrier structures (DVBs) are investigated theoretically. Analytical and numerical results demonstrate that strong resonant tunneling effect occurs in this structure and is highly dependent on the incident angle and the structure of velocity barriers. The resonant tunneling in graphene DVBs belongs to the Fabry–Pérot resonance and leads to oscillated conduction at wide energy range. It is also found that GH shifts in this structure can be enhanced by the resonant tunneling and multi-GH shift peaks with giant magnitudes can occur at these resonant energy positions. These special properties of GH shifts in graphene DVBs may have good application in lateral manipulation of electron beams and valley or spin beam splitter. 相似文献
8.
The zero bias tunneling conductance is investigated theoretically and shown to be a promising experimental tool for detecting first order phase transitions in high field superconductors. We calculate and evaluate numerically the zero bias tunneling conductance for arbitrary spin orbital mean free path. In doing the calculations we distinguish between thin films in a parallel field and high?-value materials in a perpendicular field. In the former case anomalous properties appear for sufficient long spin orbital mean free path. Finally we determine the minimum spin orbital mean free path which is compatible with a first order phase transition and show that it is much smaller than commonly believed. 相似文献
9.
We study resonant magnetotunneling in the double-barrier heterostructure in the sequential tunneling picture. The effects arising from charge buildup in the well are considered by assuming that the quasibound energy in the well varies linearly with the applied bias. Under appropriate approximations, the tunneling current density and the corresponding differential conductance are derived analytically. The results for the peak positions in differential conductance and the threshold current position are consistent with experiments. 相似文献
10.
We investigate Andreev reflection (AR) tunneling through a ferromagnet-quantum dot-superconductor (F-QD-S) system in the presence of an external ac field. The intradot spin-flip scattering in the QD is involved. Using the nonequilibrium Green function and BCS quasiparticle spectrum for superconductor, time-averaged AR conductance is formulated. The competition between the intradot spin-flip scattering and photon-assisted tunneling dominates the resonant behaviors of the time-averaged AR conductance. For weak intradot spin-flip scattering strengths, the AR conductance shows a series of equal interval resonant levels. However, the single-peak at main resonant level develops into a well-resolved double-peak resonance at a strong intradot spin-flip scattering strength. Remarkable, multiple-photon-assisted tunneling that generates photonic sideband peaks with a variable interval has been found. In addition, the AR conductance-bias voltage characteristic shows a transition between the single-peak to double-peak resonance as the ratio of the two tunneling strengths varies. 相似文献
11.
C. -Y. Yang G. -N. Tang 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(2):245-250
We study spin transport in
normal/ferromagnetic/normal/ferromagnetic.../normal
graphene superlattices, which can be realized by putting a series of
magnetic insulator bars on top of a graphene sheet. Owing to
magnetic proximity effect, local exchange splittings will be induced
in the graphene sheet, effectively forming a magnetic graphene
superlattice. The spin polarization of tunneling conductance and the
magneto resistance (MR) exhibit oscillatory behavior with the gate
voltage. The superlattice structure leads to an enhanced spin
polarization and MR ratio, making the magnetic graphene superlattice
become very promising in spintronics applications. 相似文献
12.
We investigate the resonant transmission of Dirac electrons through inhomogeneous band gap graphene with square superlattice potentials by transfer matrix method. The effects of the incident angle of the electrons, Fermi energy and substrate-induced Dirac gaps on the transmission are considered. It is found that the Dirac gap of graphene adds another degree of freedom with respect to the incident angle, the Fermi energy and the parameters of periodic superlattice potentials (i.e., the number, width and height of the barriers) for the transmission. In particular, the inhomogeneous Dirac gap induced by staggered substrates can be used to manipulate the transmission. The properties of the conductance and Fano factor at the resonant peaks are found to be affected by the gaps significantly. The results may be helpful for the practical application of graphene-based electronic devices. 相似文献
13.
We study theoretically transport properties of two-dimensional
electron gases through antiparallel magnetic-electric barrier structures. Two kinds of magnetic barrier configurations are employed: one is that the strength of the double
δ-function in opposite directions is equal and the other is that the strength is unequal. Similarities and differences of electronic transports are presented. It is found that the
transmission and the conductance depend strongly on the shape of the magnetic barrier and the height of the electric barrier. The results indicate that this system does not possess any
spin filtering and spin polarization and electron gases can
realize perfect resonant tunneling and wave-vector filtering properties.
Moreover, the strength of the effect of the inhomogeneous
magnetic field on the transport properties is discussed. 相似文献
14.
《Physica E: Low-dimensional Systems and Nanostructures》2011,43(10):2812-2815
The tight-binding method is employed to investigate the electronic properties of a square graphene quantum dot subject to an in-plane electric field (F). The electronic properties are strongly modified by tuning the field strength or altering the field direction. F will change state energies, alter energy gaps, and induce energy gap modulations. State energies show oscillatory behavior with the change of the field strength. The oscillating amplitude and period are further modulated by the change of the field direction. The field-orientation-dependent electronic properties originate in the geometrical anisotropy of the square graphene quantum dot. Moreover, the density of states (DOS), exhibiting many discrete peaks, directly reveals the characteristic of the electric-field-tunable electronic properties. The number and frequencies of DOS peaks are significantly dependent on the field strength and direction. 相似文献
15.
16.
L. V. Shtukin I. E. Berinskii D. A. Indeitsev N. F. Morozov D. Yu. Skubov 《Physical Mesomechanics》2016,19(3):248-254
The goal of this study is to construct simple electromechanical models of nanoresonators as mass detectors. A major obstacle in the achievement of sufficient measurement accuracy for the resonant frequency associated with the adsorption of additional mass onto the graphene layer is a low quality factor of the oscillatory system containing the graphene layer. A graphene resonator can be considered as an elastic system with distributed parameters. The application of the Galerkin method to study nearly resonant vibrational modes reduces the problem to considering an oscillatory system with a few degrees of freedom with pronounced nonlinear properties. These properties are, first of all, due to the nonlinear dependence of the forces produced by the electric field on the graphene deflection and, second, due to the nonlinear dependence of the graphene layer tension on its deflection. Taking into account the nonlinear properties leads to the appearance of characteristic drops in the resonance curve which allow for a more accurate resonant frequency measurement. Resonance curves with such characteristic drops can be obtained using a demonstration experimental macromodel of the resonator. Two absolutely new layouts are proposed, such as a differential resonator and resonator with parametric excitation. The oscillations excited in the differential resonator that contains two graphene layers resemble beats. In this case, small changes in the mass of the main layer correspond to significant changes in the frequency of the envelope. This effect is illustrated by oscillograms obtained for an experimental macromodel of the differential resonator. The parametric resonator has one graphene layer between two conducting surfaces. Parametric excitation of steady-state high amplitude oscillations is possible in this resonator only in a narrow frequency band close to the eigenfrequency. The band width reduces with a decrease in the quality factor of the oscillatory system. The latter fact can be useful for the improvement of eigenfrequency measurement accuracy at a low quality factor of the oscillatory system. 相似文献
17.
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
18.
We investigate the scanning tunneling spectroscopy (STS) of a two-orbital Anderson impurity
adsorbed on a metallic surface by using the numerical renormalization group (NRG) method. The density
of state of magnetic impurity and the local conduction electron are calculated. We obtain the Fano
resonance line shape in the STM conductance at zero temperature. For the impurity atom with
antiferromagnetic inter-orbital exchange interaction and a spin singlet ground state, we show that a
dip in the STM spectra around zero bias voltage regime and side peaks of spin excitation can be
observed. The spin excitation energy is proportional to the exchange interaction strength. As the
exchange interaction is ferromagnetic, the underscreened Kondo effect dominates the low energy
properties of this system, and it gives rise to drastically different STM spectra as compared with the
spin singlet case. 相似文献
19.
A comparison of the transport properties of bilayer graphene,monolayer graphene,and two-dimensional electron gas 下载免费PDF全文
We studied and compared the transport properties of charge carriers in bilayer graphene, monolayer graphene, and the conventional semiconductors (the two-dimensional electron gas (2DEG)). It is elucidated that the normal incidence transmission in the bilayer graphene is identical to that in the 2DEG but totally different from that in the monolayer graphene. However, resonant peaks appear in the non-normal incidence transmission profile for a high barrier in the bilayer graphene, which do not occur in the 2DEG. Furthermore, there are tunneling and forbidden regions in the transmission spectrum for each material, and the division of the two regions has been given in the work. The tunneling region covers a wide range of the incident energy for the two graphene systems, but only exists under specific conditions for the 2DEG. The counterparts of the transmission in the conductance profile are also given for the three materials, which may be used as high-performance devices based on the bilayer graphene. 相似文献
20.
We report a detailed theoretical study of current oscillation and dc-voltage-controlled chaotic dynamics in doped GaAs/AlAs resonant tunneling
superlattices under crossed electric and magnetic fields. When the
superlattice is biased at the negative differential velocity region, current
self-oscillation is observed with proper doping concentration. The current
oscillation mode and oscillation frequency can be affected by the dc voltage bias, doping density, and magnetic field. When an ac electric field with fixed amplitude and frequency is also applied to the system, different nonlinear properties show up in the external circuit with the change of dc voltage bias. We carefully study these nonlinear properties with different
chaos-detecting methods. 相似文献