Collaborative Research: Theory of Spin Lifetimes in Semiconductors

这个提议的主题是半导体中电子自旋衰减的理论。它的目的是了解非平衡态自旋分布一旦产生就消失所需的时间。所有的半导体材料都将被考虑，但将特别关注硅和砷化镓，这两种材料在技术上最重要。此外，所考虑的器件以影响自旋衰减的方式限制电子的运动。这一点也将予以考虑。这种自旋衰减或弛豫有多种原因。这就需要开发计算机程序来处理不同机制之间复杂的相互作用。广泛的影响在过去的50年里，大多数重要的技术进步都与电子学的进步密切相关，从物理学的角度讲，电子学就是对电子电荷的操纵。 特别是在计算机技术中，这种操作是在半导体中完成的。这种稳步的进展在过去十年左右的时间里出现了放缓的迹象，未来将取决于对电子自旋的操纵-自旋电子学领域。这个建议旨在增加我们对半导体中电子自旋行为的理论理解。从短期来看，这一领域是最有希望的技术，因为半导体中的自旋电子学将允许与当前的制造技术快速集成。 然而，关键的困难仍然存在。磁场、掺杂范围以及特别是器件的几何形状的影响引入了可以以非常显著的方式改变弛豫的复杂性。这里提出的工作集中在一些新的物理机制，我们认为是理解这些悬而未决的问题的核心。这些新的见解中最重要的是扩展态和局域态之间的自旋转移。这本身不是自旋弛豫，因为转移保持了自旋，但转移加速了自旋弛豫。第二点是由于对称性考虑和声子态密度，自旋-声子弛豫的场依赖性出乎意料地大。这些见解将被纳入计算机计算的自旋弛豫从所有机制，以实现定量的弛豫时间的理解。这将是半导体自旋弛豫理论的一个重大进展.

The subject of this proposal is the theory of the decay of electron spin in semiconductors. It aims to understand the time that it takes for non-equilibrium spin distributions to disappear once they are created. All semiconductor materials will be considered, but there will be a particular focus on silicon and gallium arsenide, which have the most technological importance. Furthermore, the devices under consideration confine the motion of the electrons in a way that affects the spin decay. This will also be taken into account. There are multiple causes for this spin decay or relaxation. This will necessitate the development of computer programs to handle the complex interaction of different mechanisms.Broad ImpactMost of the important technological advances in the last 50 years have been closely associated with the progress of electronics, which, in physical terms, is the manipulation of electronic charge. In computer technology in particular, this manipulation is done in semiconductors. This steady advance has shown signs of slowing in the last decade or so, and the future will depend on the manipulation of electronic spin - the field of spintronics. This proposal aims at increasing our theoretical understanding of the behavior of electron spins in semiconductors. This area is the most promising for technology in the short term, since spintronics in semiconductors would allow rapid integration with current manufacturing techniques.Intellectual meritMany basic mechanisms of spin relaxation in semiconductors are reasonably well understood. However, crucial difficulties remain. The effect of magnetic fields, doping ranges and particularly geometry of devices introduce complications that can change the relaxation in very significant ways. The work proposed here focuses on some novel physical mechanisms that we believe are central to understanding these unresolved issues. The most important of these novel insights is spin transfer between extended and localized states. This is not a spin relaxation in itself, since the transfer conserves spin, but the transfer accelerates spin relaxation. A second point is the unexpectedly large field dependence of the spin-phonon relaxation due to symmetry considerations and the phonon density of states. These insights will be incorporated into computer calculations of spin relaxation from all mechanisms to achieve quantitative understanding of relaxation times. This will be a major advance the theory of spin relaxation in semiconductors.