自旋相关的电子隧穿和自旋极化

研究了电子的自旋相关的隧穿和极化。在外加磁场的作用下，自旋向上的电子与自旋向下的电子具有不同的隧穿系数。当电子的自旋方向与磁场方向相反时，其隧穿概率受到磁场的抑制而变小；反之，当两平行时，电子的了隧穿系数增大。这种差异可以用本中定义的自旋极化率来表示。本对不同磁场下的自旋极化率进行了计算，结果也表明当电子的动能较小，这种自旋极化的效应越显。     

Mott散射和电子极化术

文章回顾了Mott散射过程及其物理图像，介绍了Sherman函数的定义、计算和测量，简述了探测自旋极化电子的仪器——Mott电子极化仪的一般设计，列举了获得自由极化电子的几种方法和原理．     

电磁波辐照下量子线的电子自旋极化输运性质

理论上研究Rashba自旋-轨道相互作(SOI)量子线在外电磁波辐照下的电子自旋极化输运性质.在自由电子模型下利用散射矩阵方法,发现当Rashba SOI较弱时,自旋极化率与外电磁场频率和电子入射能量无关,而当Rashba SOI较强时,自旋极化率则强烈依赖于外场频率和电子入射能量,其物理根源是Rashba SOI使子带混合引起的.此外,当电子的入射能量增加到打开另一通道阈值时,电子的透射率出现一个反常的台阶结构,这来源于电子与光子的非弹性散射而使电子在子带间的跃迁. 关键词： 量子线 电磁波 自旋极化输运 散射矩阵     

纳米管中的自旋极化

结构缺陷、掺杂等可以导致纳米管的自旋极化，而自旋极化的纳米管可以利用载流子的自旋状态作为信息载体，实现一维的自旋电子传输。具有不同自旋极化结构的纳米管，根据其电子结构、自旋极化性质和输运性质的不同，可以用于实现不同用途的自旋电子器件。很多有关自旋极化的纳米管的理论和实验工作已经展开，然而其中仍有很多物理问题有待深入研究。     

对称双势垒量子阱中自旋极化输运的时间特性

电子的隧穿时间是描述量子器件动态工作范围的重要指标. 本文考虑k³ Dresselhaus 自旋轨道耦合效应对系统哈密顿量的修正, 结合转移矩阵方法和龙格-库塔法来解含时薛定谔方程, 进而讨论了电子在非磁半导体对称双势垒结构中的透射系数及隧穿寿命等问题. 研究结果发现:由于k³ Dresselhaus 自旋轨道耦合效应使自旋简并消除, 并在时间域内得到了表达, 导致自旋向上和自旋向下电子的透射峰发生了自旋劈裂; 不同自旋取向的电子构建时间和隧穿寿命不同, 这是导致自旋极化的原因之一; 电子的自旋极化在时间上趋于稳定. 关键词： 自旋极化输运 透射系数 隧穿寿命 自旋极化率     

慢电子与亚稳态He（2^3S）弹性散射中极化势研究

本采用带有截断函数的极化势,为确定其中的可调参数,给出了一个经验公式：r↑-/r0=0.618。通过慢电子与亚稳态He(2^3S)弹性散射总截面的计算,表明本确定的极化势更准确地描述了慢电子与亚稳态He弹性散射的实际过程。     

一维铁磁/有机共轭聚合物的自旋极化研究

针对最近关于自旋注入有机体的实验研究，理论上计算了有机分子与磁性原子接触时的自旋极化现象.通过调节磁性原子的自旋劈裂强度，发现有机分子链内的自旋极化弱于金属链，但强于半导体链.同时还研究了有机分子链内自旋极化随电子-声子耦合强度的变化关系以及界面耦合的自旋相关效应. 关键词： 界面耦合 自旋极化 自旋劈裂     

液晶相位可变延迟器对自旋极化电子束极化方向的调制

讨论了液晶相位可变延迟器（liquid crystal variable retarder, LCVR）在自旋极化电子产生方面的应用.LCVR控制入射光子的偏振度，从而实现对自旋极化电子束极化方向的调制.采用LCVR代替1/4波片和Pockels盒的优点在于其对入射光方向不敏感，传输直径大，不需要机械转动即可大波长范围的延迟，且易于校准.另外，还研制了旋转检偏器，通过示波器读出，对光子偏振性进行检测并对LCVR进行校准. 关键词： 自旋极化电子源 液晶相位可变延迟器 极化方向     

自旋极化电子从铁磁金属注入半导体时自旋极化的计算

对自旋极化电子从铁磁金属通过绝缘层薄膜注入半导体时的自旋极化率与绝缘层厚度以及所加偏压的关系等作了计算.所得结果与最新实验结果相符，并发现偏压适中、绝缘层较厚时 有较大的电流自旋极化率，偏压很小时电流自旋极化率几乎为零. 关键词： 自旋极化电子注入 Slonczewski模型 隧道磁电阻 非零偏压     

利用飞秒双光子光电子发射研究GaAs(100)的自旋动力学过程

超短激光技术的发展为研究材料中的超快光动方学过程提供了重要的实验手段，也使得人们 能够更为深入地研究电子的自旋动力学行为.GaAs(100)表面由于费米钉扎而会导致能带弯曲 ，位于该区域的电子及其自旋特性将会明显不同于体相材料中的情况.利用时间分辨和自旋 分辨的双光子光电子发射技术研究了p型掺杂GaAs(100)表面的电子极化动力学过程.结果表 明，由费米钉扎而引起的能带弯曲明显影响电子的自旋弛豫过程，从实验上观察到了GaAs(1 00)表面能带弯曲区域的电子自旋翻转时间存在近2个量级的差异(从几纳秒到几十皮秒)，基 于电子-自旋交换相互作用的BAP机理在自旋弛豫过程中起着主导作用. 关键词： 光物理 自旋极化 双光子光电子发射 砷化镓     

Spin dependent 2D electron scattering by nanomagnets

The 2D scattering problem of an electron by a magnetized nanoparticle is solved in the Born approximation with account of the dipole-dipole interaction of the magnetic moments of electron and nanomagnet. The scattering amplitudes in this problem are the two-component spinors. They are obtained as functions of the electron spin orientation, the electron energy and show anisotropy in scattering angle. The initially polarized beam of electrons scattered by the nanomagnet consists of electrons with no spin flipped and spin flipped. The majority of electrons with no spin flipped are scattered by small angles. The majority electrons with spin flipped are scattered in the vicinity of the scattering angles π/2 and 3π/2. This can be used as one more method of controlling the spin currents.     

Conductance of a large point contact with Rashba effect

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     

Λ超子碎裂函数的夸克味分离

利用有非极化和极化的A和A超子产生的中微子和反中微子的深度非弹性散射,可以清晰地测量各种味的夸克变为A超子的各种非极化和极化的碎裂函数,也就是得到了碎裂函数的夸克味分离.这种方法不但适用于轻味夸克。反夸克,也适用于奇异夸克s和s.和产生A和A的极化电子的深度非弹性散射结合起来,人们就能够系统地测量或核实各种味和各种自旋的夸克的相关碎裂函数.这样的测量给有关强子的自旋结构和核子海的夸克一反夸克不对称性的各种预言提供判决性的实验.     

Measurement of single- and double-spin asymmetries in deep inelastic pion electroproduction with a longitudinally polarized target

We report the first measurement of the transverse momentum dependence of double-spin asymmetries in semi-inclusive production of pions in deep-inelastic scattering off the longitudinally polarized proton. Data have been obtained using a polarized electron beam of 5.7 GeV with the CLAS detector at the Jefferson Lab (JLab). Modulations of single spin asymmetries over the azimuthal angle between lepton scattering and hadron production planes ? have been measured over a wide kinematic range in Bjorken x and virtual photon squared four-momentum Q2. A significant nonzero sin2? single spin asymmetry was observed for the first time indicating strong spin-orbit correlations for transversely polarized quarks in the longitudinally polarized proton.     

MTV-G experiment: Probing non-standard strong gravitational field at nuclear scale using geodetic precession

A new experiment named MTV-G, probing a large electron spin-precession due to a possible strong gravitational field, which predicted by large extra dimension model, is started at TRIUMF from 2011. In an electron-nuclear scattering experiment, a strong gravitational field is tested as a large spin precession effect caused by geodetic precession predicted by general relativity theory as a result of a warped space-time around nuclei. Experimental design using spin polarized electron source and Mott-spin analyzer, commissioning experiment and the preliminary results are described.     

Collisional alignment and orientation of atomic outer shells. III. Spin-resolved excitation

The review generalizes the formalism of the first part of this series [N. Andersen, J.W. Gallagher and I.V. Hertel, Phys. Rep. 165 (1988) 1–188] on electron-atom collisions to cases where the spin polarization of the electron is investigated at least once, i.e., before and/or after the collision. In addition, the target atom may be spin polarized. The preparation of initially polarized beams and/or the analysis of photon and spin polarization in the final state significantly increase the number of cases where a “perfect scattering experiment” can be performed. The connection between the scattering amplitudes and the generalized Stokes and STU parameters is analyzed. Favorable scattering geometries for perfect experiments and possibilities for consistency checks are pointed out. Recommendations are made about directions of future work.     

Polarized deep inelastic scattering at collider energies

Spin asymmetries in deep inelastic scattering with longitudinally polarized electron and proton beams are examined. These predictions are a good testing ground for the nucleon spin structure and for the electroweak theory. Some of them will be measured in polarization experiments at future colliders.     

Dynamics of polarization buildup by spin filtering

There has been much recent research into polarizing an antiproton beam, instigated by the recent proposal from the PAX (Polarized Antiproton eXperiment) project at GSI Darmstadt. It plans to polarize an antiproton beam by repeated interaction with a polarized internal target in a storage ring. The method of polarization by spin filtering requires many of the beam particles to remain within the ring after scattering off the polarized internal target via electromagnetic and hadronic interactions. We present and solve sets of differential equations which describe the buildup of polarization by spin filtering in many different scenarios of interest to projects planning to produce high-intensity polarized beams. These scenarios are: 1) spin filtering of a fully stored beam; 2) spin filtering while the beam is being accumulated, i.e. unpolarized particles are continuously being fed into the beam; 3) the particle input rate is equal to the rate at which particles are being lost due to scattering beyond the ring acceptance angle, the beam intensity remaining constant; 4) increasing the initial polarization of a stored beam by spin filtering; 5) the input of particles into the beam is stopped after a certain amount of time, but spin filtering continues. The rate of depolarization of a stored polarized beam on passing through an electron cooler is also shown to be negligible.     

Time reversal and spatial symmetries in spin-polarized low-energy electron diffraction

Time reversal and spatial symmetries impose restrictions on spin-orbit-induced polarization effects in low-energy electron diffraction from single crystal surfaces. General predictions are derived concerning the spin polarization vector after diffraction, the scattering asymmetry vector for oppositely polarized primary beams and relations between these two quantities.     

Single spin asymmetries in the (quasi)elastic electron-proton and electron-deuteron scattering Strangeness in the nucleon and two-photon exchange amplitude

Single spin asymmetries in (quasi)elastic electron-proton and electron-deuteron scattering give insight into the structure of the nucleon. In case of a longitudinally polarized electron beam, the parity violating asymmetries can be used to determine the contribution of strange quarks to the vector form factors of the nucleon, whereas the asymmetries using a transversely polarized electron beam allow a determination of the imaginary part of the two-photon exchange amplitude which is related to the nucleon structure due to excited intermediate proton states. Both cases are presented here.