RUI: Ultrafast THz Spectroscopy of Spin Dynamics in Semiconductors

RUI：半导体自旋动力学的超快太赫兹光谱

• 批准号: 0074622
• 负责人: James Heyman
• 金额: $ 18.92万
• 依托单位: Macalester College
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-06-01 至 2003-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0074622&HistoricalAwards=false
• 关键词: RUI; Ultrafast; THz; Spectroscopy; Spin

This project will use ultrafast THz spectroscopy to study spin excitations in narrow-gap semiconductor quantum wells. These systems exhibit a large spin-orbit coupling, permitting the spin-state of carriers to be controlled with an electric field such as that from a gate contact. These systems will be investigated with a time-resolved spectroscopic probe tuned to the energy scale of the spin-orbit interaction (1-5meV). The lifetimes and energy spectra of spin excitations will be determined for a number of quantum well structures. Such measurements are made possible by the spin-orbit interaction, which will allow optical generation of carriers in a well-defined spin-state, and optical probes of the evolution of spins. Ultrafast THz spectroscopy will also be used to perform pulsed-EPR measurements at terahertz frequencies on donor electrons in InAs. The successful performance of these experiments will demonstrate the applicability of this technique to a wide range of physical systems. Terahertz frequency generation on patterned semiconductor surfaces will also be investigated. It is expected that surface patterning will boost the efficiency of generation of optically pumped THz pulses from semiconductor surfaces by about one order of magnitude. Lastly, carrier lifetimes will be investigated in picosecond carrier-lifetime materials such as low-temperature grown GaAs and radiation damaged semiconductors. Undergraduate students will participate in this research which will be performed at Macalester College and the University of Minnesota. The project will also benefit from collaboration with an industrial partner. The students will thus also acquire research experience in a setting of a major research enterprise. %%%As advances in technology push the size of transistors towards atomic dimensions, their properties will be increasingly influenced by quantum mechanics. For this reason, scientists are exploring devices that rely on quantum phenomena for their function. One such promising area involves semiconductor devices in which an electron's spin, rather than its charge, is used to control the flow of electric current. At the present time the most promising systems for realizing such semiconductor spin-transport devices are thin layers of materials such as indium arsenide and indium antimonide. Realizing these new technologies requires, however, a detailed understanding of the behavior of electron spins in these systems at ultra-short time intervals. This research is devoted to an experimental investigation of the optical properties of indium arsenide and indium antimonide by means of infrared spectroscopy at a time resolution of one trillionth of a second. Such measurements will reveal how much energy is required to change the direction of the spin in these systems, and how long the spin remains in the newly oriented state. Additional experiments will be performed to demonstrate the feasibility of pulsed magnetic resonance spectroscopy at these ultra-short time scales. This research will be conducted at Macalester College as well as at the University of Minnesota. The project will also benefit from the participation of an industrial collaborator. Undergraduate students will be engaged in this research. They will thereby acquire skills and knowledge in a forefront area of condensed matter physics and materials science. They will be prepared for advanced studies with an appreciation for the needs of advanced technology and for entry into the scientific/technological workforce.

这个项目将使用超快太赫兹光谱来研究窄禁带半导体量子阱中的自旋激发。这些系统表现出很大的自旋-轨道耦合，使得载流子的自旋态可以通过一个电场来控制，比如来自栅极接触的电场。这些系统将用时间分辨光谱探测器调谐到自旋-轨道相互作用的能量尺度(1-5 meV)进行研究。自旋激发的寿命和能谱将被确定为一些量子井结构。这样的测量是通过自旋-轨道相互作用和自旋演化的光学探测器实现的，这将允许光学产生处于定义明确的自旋态的载流子。超快太赫兹光谱还将用于在太赫兹频率下对InAs中的施主电子进行脉冲EPR测量。这些实验的成功运行将证明该技术在广泛的物理系统中的适用性。还将研究在图案化半导体表面上产生太赫兹频率的问题。预计表面图案化将把从半导体表面产生光泵浦太赫兹脉冲的效率提高约一个数量级。最后，我们将研究皮秒载流子寿命材料，如低温生长的砷化镓和辐射损伤半导体。本科生将参与这项研究，该研究将在麦卡莱斯特学院和明尼苏达大学进行。该项目还将受益于与一个行业合作伙伴的合作。因此，学生还将在大型研究企业的背景下获得研究经验。随着技术的进步将晶体管的尺寸推向原子尺寸，它们的性能将越来越受到量子力学的影响。出于这个原因，科学家们正在探索依赖量子现象实现其功能的设备。其中一个很有希望的领域涉及半导体器件，在这种器件中，电子的自旋而不是电荷被用来控制电流的流动。目前，实现这种半导体自旋输运器件的最有前途的系统是薄层材料，如砷化铟和锑化铟。然而，要实现这些新技术，需要详细了解这些系统中超短时间间隔的电子自旋行为。本文利用红外光谱技术对砷化铟和锑化铟的光学性质进行了实验研究，其时间分辨率为万亿分之一秒。这样的测量将揭示在这些系统中需要多少能量来改变自旋的方向，以及自旋保持在新取向状态的时间。还将进行其他实验，以证明脉冲磁共振光谱在这些超短时间尺度上的可行性。这项研究将在麦卡莱斯特学院和明尼苏达大学进行。该项目还将受益于一位行业合作者的参与。本科生将参与这项研究。因此，他们将获得凝聚态物理和材料科学前沿领域的技能和知识。他们将为深造做好准备，了解先进技术的需要，并进入科学/技术工作队伍。