Collaborative Research: Theory of Spin Lifetimes in Semiconductors

合作研究：半导体自旋寿命理论

• 批准号: 0524253
• 负责人: ROBERT JOYNT
• 金额: $ 15万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-01 至 2009-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0524253&HistoricalAwards=false
• 关键词: Collaborative; Research; Theory; Spin; Lifetimes

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.

本提案的主题是半导体中电子自旋衰变的理论。它的目的是了解非平衡自旋分布一旦产生就消失所需要的时间。所有的半导体材料都将被考虑，但将特别关注硅和砷化镓，它们在技术上最重要。此外，所考虑的器件以一种影响自旋衰减的方式限制了电子的运动。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，而电子学在物理上就是对电荷的操纵。特别是在计算机技术中，这种操作是在半导体中完成的。在过去的十年里，这种稳定的进步已经显示出放缓的迹象，未来将取决于对电子自旋的操纵——自旋电子学领域。这一建议旨在增加我们对半导体中电子自旋行为的理论认识。这个领域在短期内是最有前途的技术，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。智力优势半导体中自旋弛豫的许多基本机制已经相当清楚。然而，关键的困难仍然存在。磁场的影响，掺杂范围，特别是器件的几何形状会引入一些复杂的因素，这些因素会以非常显著的方式改变弛豫。这里提出的工作重点是一些新的物理机制，我们认为这是理解这些未解决问题的核心。这些新见解中最重要的是扩展态和局域态之间的自旋转移。这本身并不是自旋松弛，因为转移使自旋守恒，但是转移加速了自旋松弛。第二点是由于对称性考虑和态声子密度，自旋声子弛豫出乎意料的大场依赖。这些见解将被纳入所有机制的自旋弛豫的计算机计算中，以实现对弛豫时间的定量理解。这将是半导体中自旋弛豫理论的重大进展。