OPTICAL ORIENTATION OF SPINS IN SEMICONDUCTORS USING THE FELIX AND FELBE FREE-ELECTRON LASER FACILITIES

半导体中自旋的光学取向是一个成熟的领域，它利用了圆偏振光子吸收的选择规则。使用短脉冲激光可以获得有关自旋动力学和控制的信息。该提案主要关注窄带隙 III-V 半导体 (NGS)，因为它们具有高迁移率和耦合自旋和轨道运动的强相对论效应，为自旋电子器件（即依赖于自旋而不是电荷操纵的器件）提供了优势。所选材料具有小带隙的事实立即表明需要远红外源来激发从价带到导带的自旋。此外，在此波长范围内，人们可以使用窄带隙和宽带隙材料中的带内激发（例如掺杂样品中的传导电子）获得有关动力学的有价值的信息。内部激励很重要，例如光激发空穴会影响带间实验中的电子自旋动力学，或者如果所研究的材料具有间接能隙。该提案基于萨里大学和赫瑞瓦特大学团队之间的合作，这些团队在使用自由电子激光（FEL）设施进行超快过程的红外和光学表征方面拥有丰富的经验。我们希望聘请一名位于萨里的项目学生，在 FEL 设施、FELIX（乌得勒支）和 FELBE（德累斯顿）研究 InSb 和 InAs 的块体自旋动力学和量子阱 (QW) 结构。这项活动的一个关键方面是培训和维护英国人员使用 FEL 设施的专业知识，为达斯伯里即将到来的第四代光源 (4GLS) 做准备。总体科学目标是解决与自旋操纵相关的关键问题（自旋寿命和自旋弛豫）。该计划将与帝国理工学院和 QinetiQ（马尔文）这两个合作机构密切合作，后者将通过并行资助的活动提供一套重点系统的 NGS QW 结构。

Optical orientation of spins in semiconductors is a well established field that takes advantage of the selection rules for circularly polarised photon absorption. Using short pulsed lasers information can be gained on the spin dynamics and control. The proposal focusses mainly on narrow gap III-V semiconductors (NGSs) because they offer advantages for spintronic devices (i.e. devices that depend on the manipulation of spin rather than charge), due to their high mobility and strong relativistic effects that couple the spin and orbital motion. The fact that the materials of choice have small bandgap immediately indicates that far-infrared sources are required for excitation of spins from the valence band to the conduction band. In addition, in this wavelength range one can gain valuable information about dynamics using intraband excitation (e.g. of conduction electrons in doped samples) in both narrow and wide gap materials. Intraand excitation is important if e.g. photo-excited holes influence electron spin dynamics in interband experiments, or if the material under investigation has an indirect gap. This proposal is based on collaboration between groups at Surrey and Heriot-Watt Universities with combined experience in the use of Free Electron Laser (FEL) facilities in infrared and optical characterisation of ultrafast processes. We wish to hire a project student, based at Surrey, to study spin dynamics in bulk and quantum well (QW) structures of InSb and InAs at the FEL facilities, FELIX (at Utrecht) and FELBE (at Dresden). A key aspect of this activity will be the training and maintenance of expertise of UK personnel in the use of FEL facilities in preparation for the forthcoming Fourth Generation Light Source (4GLS) at Daresbury. The overall scientific objective is to resolve key issues related to spin manipulation (spin lifetime and spin relaxation). The programme will work closely with two partner institutions, Imperial College and QinetiQ (Malvern), who will provide a focused systematic set of NGS QW structures from parallel funded activities.