Spin Electronics Novel Optical Probe of Carrier Spin Coherence in Semiconductors

自旋电子学半导体中载流子自旋相干性的新型光学探针

• 批准号: 0224154
• 负责人: Steven Cundiff
• 金额: $ 24万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-01 至 2005-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0224154&HistoricalAwards=false
• 关键词: Spin; Electronics; Novel; Optical; Probe

This proposal was received in response to the Spin Electronics for the 21st century initiative, Program Solicitation NSF 02-036. The proposal focuses on novel optical techniques for measuring carrier spin coherence on semiconductors. Spin based electronics promise to provide increased processing speed, increased integration density and decreased power consumption as compared to traditional microelectronic devices. In addition, electronic spins in semiconductors are attractive for implementation of quantum information processing. These advances require a firm understanding of electronic spin coherence in semiconductors and the development of techniques to probe spin coherence. Previous work has shown that n-doped GaAs has a remarkably long spin coherence time, which has prompted further investigation. Semimagnetic semiconductors display much shorter spin coherences, however the stronger carrier-ion interaction makes them better candidate materials for fabrication of spin filters and related devices.The techniques developed in this project will complement the predominant technique of Faraday rotation and provide information that is not available using Faraday rotation. Of specific interest is why the Faraday rotation signal saturates for high optical excitation density. The techniques are based on transient four-wave-mixing. Specifically, by using a three pulse excitation scheme, it is possible to probe the spin coherence and generate a signal in a background free direction. A modification of this that uses the fifth order nonlinear optical response can generate a Raman-spin echo, which will remove the effects of inhomogeneous spin precession rates due, for example, to a variation in the g-factor with k-vector. The experiments will be performed on n-doped GaAs and semimagnetic semiconductors such as CdMnTe and ZnMnTe. The former samples are commercially available wafers, while the latter will be provided by collaborators at the University of Dortmund, Germany. In the latter case, initial experiments to probe the optical coherence (as opposed to spin coherence) will be performed because it is not well understood and provides important insight into carrier-ion spin scattering, which is crucial for electronically controlled ferromagnetism. Preliminary Faraday-rotation experiments will be performed on both the GaAs and semimagnetic semiconductor samples to provide a connection to experimental results from other groups. During this grant, both spin-coherence and Raman-spin echo experiments will be performed on n-doped GaAs. For the semimagnetic semiconductors, optical coherence and spin coherence experiments will be performed.

这份提案是为了响应21世纪的自旋电子学计划NSF 02-036的倡议而收到的。该提案的重点是测量半导体上载流子自旋相干性的新光学技术。与传统的微电子设备相比，基于自旋的电子设备有望提供更快的处理速度、更高的集成密度和更低的功耗。此外，半导体中的电子自旋对于实现量子信息处理很有吸引力。这些进展需要对半导体中的电子自旋相干性有一个坚实的理解，并开发探测自旋相干性的技术。前人的工作表明，n掺杂的GaAs具有非常长的自旋相干时间，这促使了进一步的研究。半磁半导体的自旋相干性要短得多，然而更强的载流子-离子相互作用使它们成为制造自旋滤光片和相关器件的更好的候选材料。本项目开发的技术将补充主要的法拉第旋转技术，并提供使用法拉第旋转所不能提供的信息。特别令人感兴趣的是为什么法拉第旋转信号因高激发密度而饱和。这些技术是基于瞬变四波混频的。具体地说，通过使用三脉冲激励方案，可以探测自旋相干性并产生无背景方向的信号。使用五阶非线性光学响应的这种修改可以产生拉曼-自旋回波，这将消除例如由于g因子随k矢量的变化而引起的不均匀自旋进动速率的影响。实验将在n掺杂的砷化镓和半磁半导体上进行，如cdMnTe和znMnTe。前者的样品可以在市场上买到，而后者将由德国多特蒙德大学的合作者提供。在后一种情况下，将进行初步的实验来探测光学相干性(与自旋相干性相反)，因为它没有被很好地理解，并提供了对电子控制的铁磁性至关重要的载流子-离子自旋散射的重要洞察。初步的法拉第旋转实验将在砷化镓和半磁半导体样品上进行，以提供与其他小组的实验结果的联系。在此期间，将对n掺杂的砷化镓进行自旋相干和拉曼自旋回波实验。对于半磁半导体，将进行光学相干和自旋相干实验。