共查询到20条相似文献,搜索用时 31 毫秒
1.
N.Y. Tang 《Journal of magnetism and magnetic materials》2009,321(15):L41
The spin-polarized tunneling current through a double barrier resonant tunneling diode (RTD) with ferromagnetic GaMnN emitter/collector is investigated theoretically. Two distinct spin splitting peaks can be observed at current-voltage (I-V) characteristics at low temperature. The spin polarization decreases with the temperature due to the thermal effect of electron density of states. When charge polarization effect is considered at the heterostructure, the spin polarization is enhanced significantly. A highly spin-polarized current can be obtained depending on the polarization charge density. 相似文献
2.
通过理论计算研究GaMnN铁磁共振隧穿二极管自旋电流输运特性.理论结果表明在电流特性曲线上出现两个明显的自旋分裂峰.该电流自旋分裂峰和相应的自旋极化随温度的升高而逐渐减小消失.当进一步考虑到GaN异质结界面极化电荷影响时,自旋向下的电流共振峰得到明显增强,同时电流的自旋极化也得到相应的提高.在一定的极化电荷条件下,可以获得较高的自旋极化电流.
关键词:
GaMnN
共振隧穿
自旋电流
极化电荷 相似文献
3.
《Current Applied Physics》2009,9(5):919-924
Different from electrons and holes in traditional inorganic semiconductors, the charge carriers in polymer semiconductors are spin polarons and spinless bipolarons. In this paper, a theoretical model is presented to describe the spin-polarized injection of electrical currents from a ferromagnetic contact into a nonmagnetic polymer semiconductor. In this model, a new relation of conductivity to concentration polarization for polymer semiconductors is introduced based on a three-channel model to describe the spin-polarized injection of electrical currents under large electrical current densities. The calculated results of the model reveal the effects of the polaron ratio, the carrier concentration polarization, the interfacial conductance, the bulk conductivity of materials, and the electrical current density, etc. on the spin polarization of electrical currents. As conclusions, the large and matched bulk conductivity of materials, the small spin-dependent interfacial conductance, the thin polymer thickness and the large enough electrical current are critical factors for upgrading the spin polarization of electrical currents in polymer semiconductors. Particularly, when the polaron ratio in polymer semiconductors approaches the concentration polarization of the ferromagnetic contact, a modest concentration polarization is sufficient for achieving a nearly complete spin-polarized injection of electrical currents. 相似文献
4.
In the framework of the Landauer-Büttiker formalism, we investigate coherent spin transport through a transverse-biased magnetic zigzag-edge graphene nanoribbon, with a temperature difference applied between the source and the drain. It is shown that a critical source temperature is needed to generate a spin-polarized current due to the presence of a forbidden transport gap. The magnitude of the obtained spin polarization exceeds 90% in a wide range of source temperatures, and its polarization direction could be changed by reversing the transverse electric field. We also find that, at fixed temperature difference, the spin-polarized current undergoes a transition from increasing to decreasing as the source temperature rises, which is attributed to the competition between the excited energy of electrons and the relative temperature difference. Moreover, by modulating the transverse electric field, the source temperature and the width of the ribbon, we can control the device to work well for generating a highly spin-polarized current. 相似文献
5.
Osterwalder J 《J Phys Condens Matter》2012,24(17):171001
Photoemitted electrons move in a vacuum; their quantum state can be completely characterized in terms of energy, momentum and spin polarization by spin-polarized photoemission experiments. A review article in this issue by Heinzmann and Dil (2012 J. Phys.: Condens. Matter 24 173001) considers whether the measured spin properties, i.e. the magnitude and direction of the spin polarization vector, can be traced back to the quantum state from which these electrons originate. The careful conclusion is that they can, which is highly relevant in view of the current interest in these experiments and their application to topological insulators, where the spin-orbit interaction produces spin-polarized surface states. 相似文献
6.
D. Conrath T. Heindorff A. Hermanni N. Ludwig E. Reichert 《Applied Physics A: Materials Science & Processing》1979,20(2):155-157
GaAs0.62P0.38 activated to negative electron affinity and irradiated with circularly polarized light of a wavelength shorter than approximately
680 nm emits electrons whose spins are mainly oriented antiparallel to the photon spins. At 650 nm a degree of electron spin
polarization around 40% is observed. The spectrum of spin polarization of the photoelectrons is similar to that known from
GaAs cathodes but is shifted to shorter wavelengths. 25 μA current of spin-polarized electrons were achieved with a 5 mW He-Ne
laser. 相似文献
7.
Watchara Liewrian I-Ming Tang Rassmidara Hoonsawat 《Physica E: Low-dimensional Systems and Nanostructures》2011,44(1):327-332
The influence of magnetic vector potential barrier (MVPB) on the spin-polarized transport of massless Dirac particles in ferromagnetic graphene is studied theoretically. The phenomenon of Klein tunneling of relativistic particles across a rectangular potential barrier prevents any of the massless fermions from being confined but they can be electrically confined by quantum dots with integrable dynamics (Bardarson et al., 2009) [36]. Utilization of only the in-plane exchange splitting in the ferromagnetic graphene cannot produce 100% spin polarization. This tunneling can be confined using the magnetic vector potential barrier, which leads to high degree of spin polarization. By combining the orbital effect and the Zeeman interaction in graphene junction, it is found that the junction mimics behavior of half-metallic tunneling junction, in which it acts as a metal to particles of one spin orientation but as an insulator or a semiconductor to those of the opposite orientation. The idea of the half-metallic tunneling junction can provide a source of ∼100% spin-polarized current, which is potentially very useful. Adjustment of the position of the Fermi level in ferromagnetic layer by placing a gate voltage on top of the ferromagnetic layer shows that reverse of the orientation of the completely spin-polarized current passing through the junction is controlled by adjusting the gate voltage. These interesting characteristics should lead to a practical gate voltage controlled spin filtering and spin-polarized switching devices as a perfect spin-polarized electron source for graphene-based spintronics. 相似文献
8.
An FS/FE/NS/FE/FS double tunnel junction is suggested to have the
ability to inject, modulate and detect the spin-polarized current
electrically in a single device, where FS is the ferromagnetic
semiconductor electrode, NS is the nonmagnetic semiconductor, and FE
the ferroelectric barrier. The spin polarization of the current
injected into the NS region can be switched between a highly
spin-polarized state and a spin unpolarized state. The high spin
polarization may be detected by measuring the tunneling
magnetoresistance ratio of the double tunnel junction. 相似文献
9.
By means of the Keldysh Green's function method, we investigate the spin-polarized electron transport in a three-terminal device, which is composed of three normal metal leads and two serially-coupled quantum dots (QDs). The Rashba spin-orbit interaction (RSOI) is also considered in one of the QDs. We show that the spin-polarized charge current with arbitrary spin polarization can be obtained because of the quantum spin interference effect arising from the Rashba spin precession phase, and it can be modulated by the system parameters such as the applied external voltages, the RSOI strength, the QD levels, as well as the dot-lead coupling strengths. Moreover, a fully spin-polarized current or a pure spin current without any accompanying charge current can also be controlled to flow in the system. Our findings indicate that the proposed model can serve as an all-electrical spin device in spintronics field. 相似文献
10.
We report a study of spin-dependent transport through a quantum dot irradiated by continuous circularly polarized light resonant to the electron-heavy hole transition. We use the nonequilibrium Green's function to calculate the spin accumulation, spin-resolved currents, and current polarization in the presence of an external bias and intradot Coulomb interaction. It is found that for a range of external biases sign reversal of the current polarization can be modulated. The system thus operates as a rectifier for spin current polarization. This effect follows from the interplay between the external irradiation and the Coulomb repulsion. The spin-polarized transport through a three-terminal device is also discussed. Spin current with high polarization could be obtained due to spin filter effect. 相似文献
11.
Electric luminescence and its circular polarization in a Co2 MnAl injector-based light emitting diode (LED) has been detected at the transition of e-A0 C , where injected spin-polarized electrons recombine with bound holes at carbon acceptors. A spin polarization degree of 24.6% is obtained at 77 K after spin-polarized electrons traverse a distance of 300 nm before they recombine with holes bound at neutral carbon acceptors in a p + -GaAs layer. The large volume of the p + -GaAs layer can facilitate the detection of weak electric luminescence (EL) from e-A 0C emission without being quenched at higher bias as in quantum wells. Moreover, unlike the interband electric luminescence in the p+ -GaAs layer, where the spin polarization of injected electrons is destroyed by a very effective electron-hole exchange scattering (BAP mechanism), the spin polarization of injected electrons seems to survive during their recombination with holes bound at carbon acceptors. 相似文献
12.
《中国物理快报》2016,(3)
We investigate theoretically the spin caloritronic transport properties of a stabie 1,3,5-triphenylverdazyl(TPV)radical sandwiched between Au electrodes through different connection fashions.Obvious spin Seebeck effect can be observed in the para-connection fashion.Furthermore,a pure spin current and a completely spin-polarized current can be realized by tuning the gate voltage.Furthermore,a 100% spin polarization without the need of gate voltage can be obtained in the meta-connection fashion.These results demonstrate that TPV radical is a promising material for spin caioritronic and spintronic applications. 相似文献
13.
C. Gould G. Schmidt G. Richter R. Fiederling P. Grabs L. W. Molenkamp 《Applied Surface Science》2002,190(1-4):395-402
So far, attempts at realizing spin-polarized current injection into a semiconductor using metallic ferromagnetic contacts have yielded unsatisfying results. In this paper, we present a simple model of diffusive transport, which shows that the principle reason for these negative results is a conductivity mismatch between the ferromagnetic contacts and the semiconductor. Moreover, we demonstrate that this problem can be addressed by using dilute magnetic semiconductor (DMS) contacts instead of metallic contacts. We present experimental results of optical measurements on a GaAs/AlGaAs diode fitted with a DMS spin injector contact. These measurements show a spin polarization of around 90% in the semiconductor. Furthermore, we discuss a novel magnetoresistance effect based on the suppression of one of the spin channels in the semiconductor which should allow the detection of a spin-polarized current by magnetoresistance measurements. 相似文献
14.
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
15.
Dependences of spin polarization on the control parameters in the spin-polarized injection through the magnetic p-n junction 下载免费PDF全文
Effective spin-polarized injection from magnetic semiconductor (MS)
to nonmagnetic semiconductor (NMS) has been highlighted in recent
years. In this paper we study theoretically the dependence of
nonequilibrium spin polarization (NESP) in NMS during spin-polarized
injection through the magnetic p-n junction. Based on the theory in
semiconductor physics, a model is established and the boundary
conditions are determined in the case of no external spin-polarized
injection and low bias. The control parameters that may influence the
NESP in NMS are indicated by calculating the distribution of spin
polarization. They are the doping concentrations, the equilibrium
spin polarization in MS and the bias. The effective spin-polarized
injection can be realized more easily by optimizing the above
parameters. 相似文献
16.
R. N. Gurzhi A. N. Kalinenko A. I. Kopeliovich A. V. Yanovsky 《Journal of Experimental and Theoretical Physics》2007,105(1):149-151
Spin injection from a ferromagnetic metal into a semiconductor driven by a constant phonon flow is considered. It is shown that diffusive (as opposed to electrical) spin injection gives rise to a highly spin-polarized current through the semiconductor. In other words, phonon-wind-driven injection under certain conditions eliminates the conductivity mismatch responsible for reduced spin polarization of the electric current injected from a ferromagnetic metal into a semiconductor. 相似文献
17.
We study the spin transport in bilayer graphene nanoribbons (BGNs) in the presence of Rashba spin-orbit interaction (SOI) and external gate voltages. It is found that the spin polarization can be significantly enhanced by the interlayer asymmetry or longitudinal mirror asymmetry produced by external gate voltages. Rashba SOI alone in BGNs can only generate current with spin polarization along the in-plane y direction, but the polarization components can be found along the x, y and z directions when a gate voltage is applied. High spin polarization with flexible orientation is obtained in the proposed device. Our findings shed new light on the generation of highly spin-polarized current in BGNs without external magnetic fields, which could have useful applications in spintronics device design. 相似文献
18.
Consistency in formulation of spin current and torque associated with a variance of angular momentum
Based on the Noether's theorem, we develop systematically and rigorously the spin-dependent formulation of the conservation laws. The effect of the electronic polarization due to the spin-orbit coupling is included in the Maxwell equations. The polarization is related to the antisymmetric components of spin current, and it provides a possibility to measure the spin current directly. The variances of spin and orbit angular momentum currents imply a torque on the "electric dipole" associated with the moving electron. The dependencies of the torque on the polarization and the force on the motions of spin-polarized electrons in a two-dimensional electron gas with the Rashba spin-orbit coupling are discussed. 相似文献
19.
We predict theoretically the optical signatures of spin polarization of carriers in self-assembled quantum dots. The emission spectra are mapped out as a function of increasing electron spin polarization for a fixed number of electrons and holes. The spin-polarized spectra are determined using exact diagonalization techniques for up to 12 particles, corresponding to two lowest filled shells. We predict that the spin polarization leads to photon polarization, to redshifts of emission lines due to excess exchange interactions among the spin-polarized electrons, and to a complete breakup of emission lines for spin-polarized electronic shells. 相似文献
20.
Using the tight-binding model approximation, this paper investigates theoretically spin-dependent quantum transport through an Aharonov-Bohm (AB) interferometer. An external magnetic field is applied to produce the spinpolarization and spin current. The AB interferometer, acting as a spin splitter, separates the opposite spin polarization current. By adjusting the energy and the direction of the magnetic field, large spin-polarized current can be obtained. 相似文献