共查询到20条相似文献,搜索用时 125 毫秒
1.
2.
自旋极化电子碰撞谱仪的研制进展 总被引:1,自引:1,他引:0
与电子自旋相关的效应在散射过程中起着十分重要的作用,但却常常被较强的库仑相互作用所淹没,使得以自然电子为探针的散射实验很难对其进行直接观测.以极化电子作为探针,研制极化电子碰撞谱仪,将为开展自旋相关效应的实验研究奠定基础.本文简述了极化电子与原子分子碰撞研究的意义,并介绍了清华大学物理系极化物理实验室自行开发的GaAs极化电子源及基于该极化电子源的碰撞谱仪的研制情况. 相似文献
3.
与电子自旋相关的效应在散射过程中起着十分重要的作用,但却常常被较强的库仑相互作用所淹没,使得以自然电子为探针的散射实验很难对其进行直接观测。以极化电子作为探针,研制极化电子碰撞谱仪,将为开展自旋相关效应的实验研究奠定基础。本简述了极化电子与原子分子碰撞研究的意义,并介绍了清华大学物理系极化物理实验室自行开发的GaAs极化电子源及基于该极化电子源的碰撞谱仪的研制情况。 相似文献
4.
5.
6.
7.
8.
9.
10.
Ⅲ族金属单硫化物因其优越的光电和自旋电子特性而备受关注,实现对其自旋性质的有效调控是发展器件应用的关键.本文采用密度泛函理论系统地研究了GaSe表面Fe原子吸附体系的几何构型及自旋电子特性.Fe/GaSe体系中Fe吸附原子与最近邻Ga,Se原子存在较强的轨道耦合效应,使体系呈现100%自旋极化的半金属性.其自旋极化贡献主要来源于Fe-3d电子的转移及Fe-3d,Se-4p和Ga-4p轨道杂化效应.对于Fe双原子吸附体系,两Fe原子之间的自旋局域导致原本从Fe转移至GaSe的自旋极化电荷量减少,从而费米能级附近的单自旋通道转变为双自旋通道,费米能级处的自旋极化率转变为0.研究结果揭示了Fe_n/GaSe吸附体系自旋极化特性的形成和转变机制,可为未来二维自旋纳米器件的设计与构建提供参考. 相似文献
11.
I. V. Kukushkin K. von Klitzing K. Eberl 《Physica E: Low-dimensional Systems and Nanostructures》1998,1(1-4)
The spin configuration of the ground state of a two-dimensional electron system is investigated for different FQHE states from an analysis of circular polarization of time-resolved luminescence. The method clearly distinguishes between fully spin polarized, partially spin polarized and spin unpolarized FQHE ground states. We demonstrate that FQHE states which are spin unpolarized or partially polarized at low magnetic fields become fully spin polarized at high fields. Temperature dependence of the spin polarization reveals a nonmonotonic behavior at
. At
and
the electron system is found to be fully spin polarized. This result does not indicate the existence of any skyrmionic excitations in high magnetic field limit. However, at
the observed spin depolarization of electron system at
and
becomes broader for lower magnetic fields, so that full spin polarization remains only in a small vicinity of
. Such a behavior could be considered as a precursor of skirmionic depolarization, which would dominate for smaller ratios between Zeeman and Coulomb energies.We demonstrate that the spin polarization of 2D-electron system at
and
can be strongly affected by hyperfine interaction between electrons and optically spin-oriented nuclears. This result is due to the fact that hyperfine interaction can both enhance and suppress effective Zeeman splitting in fixed external magnetic field. 相似文献
12.
Passive magnetic shielded spin polarized electron source with optical electron polarimeter 下载免费PDF全文
A new GaAs(100) spin polarized electron source with an optical
polarimeter, which is employed in the field of polarized electron
and gas atom collision, is presented in detail. The apparatus is
passive-magnetic-shielded by a box and a cylinder made of
nickel--iron--molybdenum soft magnetic alloy without Helmholtz coil
arrangement. And a uniformly distributed residual magnetic field of
less than 5×10-7,T is obtained near the collision area. The
spin polarized electron beam is transmitted and focused onto
collision point from photocathode by a set of electron optics with
more than 25% transmission 95cm distance through an 1mm
diameter aperture. Construction and operation of the apparatus, such
as vacuum and magnetic shielding system, photocathode, laser optics,
electron optics and polarimeter are discussed. The polarization of
the spin polarized electron beam is determined to be 30.8\pm3.5%
measured with a He optical polarimeter. 相似文献
13.
14.
We study the scattering of an electron of a 2DEG through a large point contact separating a region where the electrons are free and a region where the Rashba spin-orbit coupling is present. The scattering depends dramatically on the electron incidence angle showing double refraction within the Rashba region. For incidence not normal to the interface the electron spin state is not conserved. The calculated conductance exhibits an oscillating behavior as a function of spin state of the incident electrons with different spin down and spin up currents. Our model describes both a ferromagnetic semimetallic source and a simple metallic injection electrode. In the first case the electrons are injected in a pure spin state and in the second one they are unpolarized, that is in a statistical mixture of spin up and down states. In both the cases the passage through the large point contact produces spin polarized currents.Received: 30 July 2003, Published online: 23 December 2003PACS:
85.75.Hh Spin polarized field effect transistors - 72.25.-b Spin polarized transport - 73.23.Ad Ballistic transport 相似文献
15.
Schmalbuch K Göbbels S Schäfers P Rodenbücher Ch Schlammes P Schäpers T Lepsa M Güntherodt G Beschoten B 《Physical review letters》2010,105(24):246603
Optical absorption of circularly polarized light is well known to yield an electron spin polarization in direct band gap semiconductors. We demonstrate that electron spins can even be generated with high efficiency by absorption of linearly polarized light in InxGa(1-x)As. By changing the incident linear polarization direction we can selectively excite spins in both polar and transverse directions. These directions can be identified by the phase during spin precession using time-resolved Faraday rotation. We show that the spin orientations do not depend on the crystal axes suggesting an extrinsic excitation mechanism. 相似文献
16.
A SPLEEM (spin polarized low energy electron microscope) has been designed with a numerical simulation of electrostatic and magnetic field distributions and electron ray trajectories. Highly (more than 90%) spin polarized electron source has been used. A Wien type spin manipulator and a magnetic lens type spin rotator are used to align spin direction. A magnetic field free objective lens is designed to observe magnetic domain structure of magnetic materials. High or low magnification mode can be selected by using a combined electrostatic and magnetic objective lens for a high spatial resolution and a wide imaging area observation. An electrostatic mirror aberration corrector is installed after the image forming objective lens. A double deflection 45° beam separator is used to bend the direction of electrons from the source to the objective lens and from the objective lens to the mirror aberration corrector. 相似文献
17.
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
18.
Saha D Siddiqui L Bhattacharya P Datta S Basu D Holub M 《Physical review letters》2008,100(19):196603
The spin dynamics of dilute paramagnetic impurities embedded in a semiconductor GaAs channel of a conventional lateral spin valve has been investigated. It is observed that the electron spin of paramagnetic Mn atoms can be polarized electrically when driven by a spin valve in the antiparallel configuration. The transient current through the MnAs/GaAs/MnAs spin valve bears the signature of the underlying spin dynamics driven by the exchange interaction between the conduction band electrons in GaAs and the localized Mn electron spins. The time constant for this interaction is observed to be dependent on temperature and is estimated to be 80 ns at 15 K. 相似文献
19.
A quantum dot spin light emitting diode provides a test of carrier spin injection into a qubit and a means for analyzing carrier spin injection and local spin polarization. Even with 100% spin-polarized carriers the emitted light may be only partially circularly polarized due to the geometry of the dot. We have calculated carrier polarization-dependent optical matrix elements for InAs/GaAs self-assembled quantum dots (SAQDs) for electron and hole spin injection into a range of quantum dot sizes and shapes, and for arbitrary emission directions. Calculations for typical SAQD geometries with emission along [110] show light that is only 5% circularly polarized for spin states that are 100% polarized along [110]. Measuring along the growth direction gives near unity conversion of spin to photon polarization and is the least sensitive to uncertainties in SAQD geometry. 相似文献
20.
We report on the first energy-resolved (retarding field mode) spin polarized photoemission measurement from a Ni(111) single crystal using synchrotron radiation from the ACO storage ring at LURE(ORSAY) It is shown that exchange effects can be detected for electron states well below the Fermi energy and that spin polarized, constant-initial-state spectroscopy of ferromagnets using synchrotron radiation is feasible. 相似文献