Time-Resolved Studies of Orbital Angular Momentum

轨道角动量的时间分辨研究

• 批准号: 1206270
• 负责人: James Kikkawa
• 金额: $ 36万
• 依托单位: University of Pennsylvania
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-01 至 2017-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1206270&HistoricalAwards=false
• 关键词: Time; Resolved; Studies; Orbital; Angular

****TECHNICAL ABSTRACT****Over the past 15 years, optical tools to study the time evolution of electronic spin angular momentum have made central contributions to the development of spintronics, a field of study aimed at exploiting the spin degree of freedom of delocalized electrons for classical and quantum information processing and storage in the solid state. But recent times have brought accelerating interest in new classes of materials for which orbital angular momentum becomes the central player. In this proposal the PI introduces an analogous class of ultrafast optical spectroscopies aimed at probing the dynamics of orbital angular momentum in solids. Using optical vortex beams carrying orbital angular momentum, superpositions of these beams, and holographic gratings to manipulate and separate their spatial character, the PI will construct experiments to study the dynamics of optically-excited orbital angular momentum. If successful this project will introduce a valuable tool for studying the salient dynamical features of an emerging class of orbitally coherent materials such as graphene and topological insulators. In addition to training graduate students in advanced optical techniques, this project will also strive to increase the participation and visibility of underrepresented scientists as mentors in a shared equipment facility.****NON-TECHNICAL ABSTRACT****It is no surprise to most people that when a wire is connected across the terminals of a battery, electrical current will flow. And secondary school physics courses teach students that when a magnet is waved nearby a closed loop of wire, current flows in the loop. Electrical generators, for example, utilize this effect to convert mechanical energy into electricity. But when electrical circuits become very small, another entirely different behavior is possible, which has its origins in the wave nature of the electron. Similar to the way quantum mechanics forces atomic orbitals to have discrete energies, nanoscale puddles of electrons in a material cannot occupy an arbitrary configuration. If the puddle is sufficiently small, then the quantum mechanical wave of an electron must smoothly connect to itself in going around the puddle. As a result, the puddle carries small quantum mechanical currents even when the relative position and orientation of an external magnet is held stationary. In this project, the PI will introduce an entirely new type of laser spectroscopy that excites such quantum mechanical currents in a solid and monitors their time evolution. If successful, this project will use these responses to identify solid state materials capable of storing quantum mechanical information in the rotary motion of electrons, with applications to classical and quantum mechanical devices. In addition to training graduate students in advanced optical techniques, this project will also increase the participation and visibility of underrepresented scientists as mentors in a shared equipment facility.

****技术摘要****在过去的15年中，研究电子自旋角动量的时间演化的光学工具对自旋电子学的发展做出了重要贡献，自旋电子学是一个旨在利用离域电子的自旋自由度来处理和存储固体中的经典和量子信息的研究领域。但近年来，人们对轨道角动量成为核心因素的新材料越来越感兴趣。在这个提议中，PI引入了类似的超快光谱学，旨在探测固体中轨道角动量的动力学。PI将利用携带轨道角动量的光学涡旋光束、这些光束的叠加以及全息光栅来操纵和分离它们的空间特征，构建实验来研究光激发轨道角动量的动力学。如果成功，该项目将为研究新兴轨道相干材料（如石墨烯和拓扑绝缘体）的显著动力学特征引入一个有价值的工具。除了在先进光学技术方面培训研究生外，该项目还将努力提高代表性不足的科学家作为导师在共享设备设施中的参与度和可见度。****非技术摘要****对于大多数人来说，当一根电线连接在电池的两端时，电流就会流动。中学物理课程告诉学生，当磁铁在一个闭合的线圈附近摆动时，电流就会在线圈中流动。例如，发电机利用这种效应将机械能转化为电能。但是当电路变得非常小时，另一种完全不同的行为是可能的，它起源于电子的波动性质。类似于量子力学迫使原子轨道具有离散能量的方式，材料中的纳米级电子水坑不能占据任意配置。如果水坑足够小，那么电子的量子力学波必须在水坑周围平滑地与自身连接。因此，即使外部磁铁的相对位置和方向保持不变，水坑也会携带少量量子力学电流。在这个项目中，PI将引入一种全新的激光光谱学，在固体中激发这种量子力学电流，并监测它们的时间演变。如果成功，该项目将利用这些响应来识别能够在电子旋转运动中存储量子力学信息的固态材料，并将其应用于经典和量子力学设备。除了培训研究生掌握先进的光学技术外，该项目还将提高代表性不足的科学家作为导师在共享设备设施中的参与度和可见度。