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.

该项目将使用Ultrafast THZ光谱学来研究狭窄的半导体量子井中的旋转激发。这些系统表现出大型自旋轨道耦合，允许载体的自旋状态由电场控制，例如从栅极接触中。这些系统将通过时间分辨的光谱探针进行研究，并调谐到自旋轨道相互作用的能量尺度（1-5MEV）。对于许多量子井结构，将确定自旋激发的寿命和能量光谱。自旋轨道相互作用使此类测量成为可能，这将允许在定义明确的自旋状态下进行光学生成载体，以及旋转演变的光学探针。 超快THZ光谱也将用于在INAS中的供体电子上对Terahertz频率进行脉冲-EPR测量。这些实验的成功性能将证明该技术对广泛的物理系统的适用性。还将研究图案的半导体表面上的Terahertz频率产生。预计表面模式将提高半导体表面上光泵送的Thz脉冲的产生效率约一个数量级。 最后，载体寿命将在千秒携带者的材料中进行研究，例如低温种植的GAA和辐射损坏的半导体。 本科生将参加这项研究，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工业合作伙伴的合作。因此，学生还将在一家大型研究企业的环境中获得研究经验。 %%％随着技术的进步将晶体管的大小推向原子维度，它们的性质将越来越受量子力学的影响。 因此，科学家正在探索依靠量子现象来功能的设备。这样一个有希望的区域涉及半导体设备，其中电子的自旋而不是电荷用于控制电流的流动。目前，实现这种半导体自旋传输设备的最有前途的系统是薄层材料（例如砷化胺和二胺）的材料层。但是，意识到这些新技术需要在超短时间间隔中详细了解这些系统中电子旋转的行为。 这项研究致力于通过红外光谱法以一万分之一的时间分辨率通过红外光谱进行实验研究。这样的测量将揭示需要多少能量才能改变这些系统中旋转方向，以及旋转在新定向状态中保持多长时间。将进行其他实验，以证明在这些超短时间尺度上脉冲磁共振光谱的可行性。 这项研究将在Macalester学院以及明尼苏达大学进行。该项目还将受益于工业合作者的参与。 本科生将从事这项研究。 因此，他们将在凝结物物理和材料科学的最前沿领域中获取技能和知识。 他们将为高级研究做好准备，并感谢先进技术的需求以及进入科学/技术劳动力的需求。