共查询到20条相似文献,搜索用时 15 毫秒
1.
Spin current and its heat effect in a multichannel quantum wire with Rashba spinben orbit coupling 下载免费PDF全文
Using the perturbation method, we theoretically study the spin current and its heat effect in a multichannel quantum wire with Rashba spin—orbit coupling. The heat generated by the spin current is calculated. With the increase of the width of the quantum wire, the spin current and the heat generated both exhibit period oscillations with equal amplitudes. When the quantum-channel number is doubled, the oscillation periods of the spin current and of the heat generated both decrease by a factor of 2. For the spin current js,xy, the amplitude increases with the decrease of the quantum channel; while the amplitude of the spin current js,yx remains the same. Therefore we conclude that the effect of the quantum-channel number on the spin current js,xy is greater than that on the spin current js,yx. The strength of the Rashba spin—orbit coupling is tunable by the gate voltage, and the gate voltage can be varied experimentally, which implies a new method of detecting the spin current. In addition, we can control the amplitude and the oscillation period of the spin current by controlling the number of the quantum channels. All these characteristics of the spin current will be very important for detecting and controlling the spin current, and especially for designing new spintronic devices in the future. 相似文献
2.
Pure spin polarized transport based on Rashba spin orbit interaction through the Aharonov Bohm interferometer embodied four-quantum-dot ring 下载免费PDF全文
The spin-polarized linear conductance spectrum and current-voltage characteristics in a four-quantum-dot ring embodied into Aharonov-Bohm (AB) interferometer are investigated theoretically by considering a local Rashba spin-orbit interaction. It shows that the spin-polarized linear conductance and the corresponding spin polarization are each a function of magnetic flux phase at zero bias voltage with a period of 2π, and that Hubbard U cannot influence the electron transport properties in this case. When adjusting appropriately the structural parameter of inter-dot coupling and dot-lead coupling strength, the electronic spin polarization can reach a maximum value. Furthermore, by adjusting the bias voltages applied to the leads, the spin-up and spin-down currents move in opposite directions and pure spin current exists in the configuration space in appropriate situations. Based on the numerical results, such a model can be applied to the design of a spin filter device. 相似文献
3.
Generating and reversing spin accumulation by temperature gradient in a quantum dot attached to ferromagnetic leads 下载免费PDF全文
We propose to generate and reverse the spin accumulation in a quantum dot (QD) by using the temperature difference between the two ferromagnetic leads connected to the dot. The electrons are driven purely by the temperature gradient in the absence of an electric bias and a magnetic field. In the Coulomb blockade regime, we find two ways to reverse the spin accumulation. One is by adjusting the QD energy level with a fixed temperature gradient, and the other is by reversing the temperature gradient direction for a fixed value of the dot level. The spin accumulation in the QD can be enhanced by the magnitudes of both the leads’ spin polarization and the asymmetry of the dot-lead coupling strengths. The present device is quite simple, and the obtained results may have practical usage in spintronics or quantum information processing. 相似文献
4.
Spin current and its heat effect in a multichannel quantum wire with Rashba spin-orbit coupling 下载免费PDF全文
Using the perturbation method,we theoretically study the spin current and its heat effect in a multichannel quantum wire with Rashba spin-orbit coupling.The heat generated by the spin current is calculated.With the increase of the width of the quantum wire,the spin current and the heat generated both exhibit period oscillations with equal amplitudes.When the quantum-channel number is doubled,the oscillation periods of the spin current and of the heat generated both decrease by a factor of 2.For the spin current j s,xy,the amplitude increases with the decrease of the quantum channel;while the amplitude of the spin current j s,yx remains the same.Therefore we conclude that the effect of the quantum-channel number on the spin current j s,xy is greater than that on the spin current j s,yx.The strength of the Rashba spin-orbit coupling is tunable by the gate voltage,and the gate voltage can be varied experimentally,which implies a new method of detecting the spin current.In addition,we can control the amplitude and the oscillation period of the spin current by controlling the number of the quantum channels.All these characteristics of the spin current will be very important for detecting and controlling the spin current,and especially for designing new spintronic devices in the future. 相似文献
5.
Spin and valley half metal induced by staggered potential and magnetization in siliceneSpin and valley half metal induced by staggered potential and magnetization in siliceneSpin and valley half metal induced by staggered potential and magnetization in silicene 下载免费PDF全文
We investigate the electron transport in silicene with both staggered electric potential and magnetization; the latter comes from the magnetic proximity effect by depositing silicene on a magnetic insulator. It is shown that the silicene could be a spin and valley half metal under appropriate parameters when the spin-orbit interaction is considered; further, the filtered spin and valley could be controlled by modulating the staggered potential or magnetization. It is also found that in the spin-valve structure of silicene, not only can the antiparallel magnetization configuration significantly reduce the valve-structure conductance, but the reversing staggered electric potential can cause a high-performance magnetoresistance due to the spin and valley blocking effects. Our findings show that the silicene might be an ideal basis for the spin and valley filter analyzer devices. 相似文献
6.
We analyse the influence of an inhomogenous microwave field on the coherence of atom ensembles. Two methods are proposed to suppress the dephasing generated by the inhomogenous Rabi frequency. One of them is realized by using a spin echo, and the other one is based on the identical spin rotation effect. The calculation results show that the contrast of a signal acquired in experiment can be improved by using the two methods. Their advantages and drawbacks are discussed. We hope they can be used to improve the contrast of experimental signals in situations where microwave fields are very inhomogenous. Finally, we discuss the case of a continuous working microwave field and show that the dipole force raised with the inhomogeneity can be eased by spin flip. 相似文献
7.
Modulation and enhancement of photonic spin Hall effect with graphene in broadband regions 下载免费PDF全文
The photonic spin Hall effect(SHE)holds great potential applications in manipulating spin-polarized photons.However,the SHE is generally very weak,and previous studies of amplifying photonic SHE were limited to the incident light in a specific wavelength range.In this paper,we propose a four-layered nanostructure of prism-graphene-air-substrate,and the enhanced photonic SHE of reflected light in broadband range of 0 THz–500 THz is investigated theoretically.The spin shift can be dynamically modulated by adjusting the thickness of air gap,Fermi energy of graphene,and also the incident angle.By optimizing the structural parameter of this structure,the giant spin shift(almost equal to its upper limit,half of the incident beam waist)in broadband range is achieved,covering the terahertz,infrared,and visible range.The difference is that in the terahertz region,the Brewster angle corresponding to the giant spin shift is larger than that of infrared range and visible range.These findings provide us with a convenient and effective way to tune the photonic SHE,and may offer an opportunity for developing new tunable photonic devices in broadband range. 相似文献
8.
A spin device with three normal metal leads via triple quantum dot in the presence of Rashba spin-orbit interaction is proposed, which is free from magnetic field or magnetic material. Using nonequilibrium Green's function technique, we investigate the spin current through the three-quantum-dot device. It is found that the spin current can be affected by the strength of the Rashba spin-orbit interaction, Coulomb interaction, the energy of the quantum dot and the bias voltage of the lead. The periodic oscillation of spin current can be controlled by tuning the Rashba spin-orbit interaction. 相似文献
9.
Spontaneous Josephson spin current in triplet superconductor/ferromagnet/triplet superconductor junctions 下载免费PDF全文
This paper theoretically studies Josephson spin current
through triplet superconductor/ferromagnet/triplet superconductor
junctions. At the ferromagnet/superconductor interfaces, the
ferromagnetic scattering potential gives rise to coupling between
the Andreev bound states and lifts their spin degeneracy. These
spin-split Andreev states carry the Josephson spin current through
the junctions. The generated spin supercurrent can be controlled by
the magnetization of a ferromagnetic thin layer and bias voltage
across the junctions. 相似文献
10.
Spin-dependent electron transport of a waveguide with Rashba spin--orbit coupling in an electromagnetic field 下载免费PDF全文
We investigate theoretically the spin-dependent electron
transport in a straight waveguide with Rashba spin--orbit coupling
(SOC) under the irradiation of a transversely polarized
electromagnetic (EM) field. Spin-dependent electron conductance and
spin polarization are calculated as functions of the emitting
energy of electrons or the strength of the EM field by adopting the mode
matching approach. It is shown that the spin polarization can be
manipulated by external parameters when the strength of Rashba
SOC is strong. Furthermore, a sharp step structure is found to exist
in the total electron conductance. These results can be understood
by the nontrivial Rashba subbands intermixing and the electron
intersubband transition when a finite-range transversely polarized
EM field irradiates a straight waveguide. 相似文献
11.
We investigate the spin accumulation in a double quantum dot Aharonov-Bohm (AB) interferometer in which both the Rashba spin-orbit (RSO) interaction and intradot Coulomb interaction are taken into account. Due to the existence of the RSO interaction, the electron, flowing through different arms of the AB ring, will acquire a spin-dependent phase factor in the tunnel-coupling strengths. This phase factor will induce various interesting interference phenomena. It is found that the electrons of the different spin directions can accumulate in the two dots by properly adjusting the bias and the intradot level with a fixed RSO interaction strength. Moreover, both the magnitude and direction of the spin accumulation in each dot can be conveniently controlled and tuned by the gate voltage acting on the dot or the bias on the lead. 相似文献
12.
All commercial electron spin polarimeters work in single channel mode, which is the bottleneck of researches by spin-resolved photoelectron spectroscopy. By adopting the time inversion antisymmetry of the magnetic field, we developed a multichannel spin polarimeter based on normal incident very low energy electron diffraction (VLEED). The key point to achieve the multi-channel measurements is the spatial resolution of the electron optics. The test of the electron optics shows that the designed spatial resolution can be achieved and an image type spin polarimeter with 100 times 100, totally ten thousand channels is possible to be realized. 相似文献
13.
We investigate the electron transport in silicene with both staggered electric potential and magnetization; the latter comes from the magnetic proximity effect by depositing silicene on a magnetic insulator. It is shown that the silicene could be a spin and valley half metal under appropriate parameters when the spin–orbit interaction is considered; further, the filtered spin and valley could be controlled by modulating the staggered potential or magnetization. It is also found that in the spin-valve structure of silicene, not only can the antiparallel magnetization configuration significantly reduce the valve-structure conductance, but the reversing staggered electric potential can cause a high-performance magnetoresistance due to the spin and valley blocking effects. Our findings show that the silicene might be an ideal basis for the spin and valley filter analyzer devices. 相似文献
14.
Amorphous silicon oxide containing nanocrystalline silicon grain(nc-SiO_x:H) films are prepared by a plasmaenhanced chemical vapor deposition technique at different negative substrate bias voltages.The influence of the bias voltage applied to the substrate on the microstructure is investigated.The analysis of x-ray diffraction spectra evidences the in situ growth of nanocrystalline Si.The grain size can be well controlled by varying the substrate bias voltage,and the largest size is obtained at 60 V.Fourier transform infrared spectra studies on the microstructure evolutions of the nc-SiO_x:H films suggest that the absorption peak intensities,which are related to the defect densities,can be well controlled.It can be attributed to the fact that the negative bias voltage provides a useful way to change the energies of the particles in the deposition process,which can provide sufficient driving force for the diffusion and movement for the species on the growing surface and effectively passivate the dangling bonds.Also the larger grain size and lower band gap,which will result in better photosensitivity,can also be obtained with a moderate substrate bias voltage of 60 V. 相似文献
15.
Effect of substrate bias on negative bias temperature instability of ultra-deep sub-micro p-channel metal--oxide--semiconductor field-effect transistors 下载免费PDF全文
The effect of substrate bias on the degradation during applying a
negative bias temperature (NBT) stress is studied in this paper.
With a smaller gate voltage stress applied, the degradation of
negative bias temperature instability (NBTI) is enhanced, and there
comes forth an inflexion point. The degradation pace turns larger
when the substrate bias is higher than the inflexion point. The
substrate hot holes can be injected into oxide and generate
additional oxide traps, inducing an inflexion phenomenon. When a
constant substrate bias stress is applied, as the gate voltage
stress increases, an inflexion comes into being also. The higher
gate voltage causes the electrons to tunnel into the substrate from
the poly, thereby generating the electron--hole pairs by impact
ionization. The holes generated by impact ionization and the holes
from the substrate all can be accelerated to high energies by the
substrate bias. More additional oxide traps can be produced, and
correspondingly, the degradation is strengthened by the substrate
bias. The results of the alternate stress experiment show that the
interface traps generated by the hot holes cannot be annealed, which
is different from those generated by common holes. 相似文献
16.
A Silicon Cluster Based Single Electron Transistor with Potential Room-Temperature Switching 下载免费PDF全文
We demonstrate the fabrication of a single electron transistor device based on a single ultra-small silicon quantum dot connected to a gold break junction with a nanometer scale separation. The gold break junction is created through a controllable electromigration process and the individual silicon quantum dot in the junction is determined to be a Si_(170) cluster. Differential conductance as a function of the bias and gate voltage clearly shows the Coulomb diamond which confirms that the transport is dominated by a single silicon quantum dot. It is found that the charging energy can be as large as 300 meV, which is a result of the large capacitance of a small silicon quantum dot(~1.8 nm). This large Coulomb interaction can potentially enable a single electron transistor to work at room temperature. The level spacing of the excited state can be as large as 10 meV, which enables us to manipulate individual spin via an external magnetic field. The resulting Zeeman splitting is measured and the g factor of 2.3 is obtained, suggesting relatively weak electron-electron interaction in the silicon quantum dot which is beneficial for spin coherence time. 相似文献
17.
We propose and analyze an efficient high-dimensional quantum state transfer protocol in an XX coupling spin network with a hypercube structure or chain structure. Under free spin wave approximation, unitary evolution results in a perfect high-dimensional quantum swap operation requiring neither external manipulation nor weak coupling. Evolution time is independent of either distance between registers or dimensions of sent states, which can improve the computational efficiency. In the low temperature regime and thermodynamic limit, the decoherence caused by a noisy environment is studied with a model of an antiferromagnetic spin bath coupled to quantum channels via an Ising-type interaction. It is found that while the decoherence reduces the fidelity of state transfer, increasing intra-channel coupling can strongly suppress such an effect. These observations demonstrate the robustness of the proposed scheme. 相似文献
18.
《中国光学快报(英文版)》2017,(11)
A scheme of triangular-shaped pulses with full duty cycle generation is proposed and analyzed.Benefiting from the feature of orthogonal polarization,two approximate sinusoidal signals on different polarization states can be combined without inducing coherent interference.By tuning the time mismatching between the two signals,an approximately triangular-shaped profile can be obtained in the optical intensity.It is found that the modulation index β is no longer a fixed one,but it can be aligned within a proper range of 0.92 to 1.57.To evaluate the proposal,impacts of radio frequency voltage fluctuation,bias voltage drift,and time mismatching are discussed.Within the defined fitting error(η≤ 3%),the tolerable range of the modulation index,time mismatching,and voltage have been found,which insures a simple operation in practice. 相似文献
19.
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
20.
A double T-shaped device model is constructed to investigate the spin polarized current injection and transportation properties in organic semiconductors.Based on the spin diffusion theory and Ohm’s law and considering the different charge-spin relationship of the special carriers in organic semiconductors,the current spin polarization has been obtained.Effects of the branch current ratio and the polaron proportion on the spin polarized current injection efficiency are studied.From the calculation,it is found that the improvement of the spin polarized current injection efficiency can be obtained by adjusting the branch current ratio;moreover,high polaron proportion in organic semiconductors is beneficial for obtaining high current spin polarization. 相似文献