Time-Resolved Studies of Orbital Angular Momentum

* 技术摘要 * 在过去的15年里，研究电子自旋角动量随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进行经典和量子信息处理以及固态存储的研究领域。但最近，人们对轨道角动量成为核心角色的新材料类别产生了越来越大的兴趣。 在这个提议中，PI介绍了一种类似的超快光谱学，旨在探测固体中轨道角动量的动力学。 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性，PI将构建实验来研究光激发轨道角动量的动力学。 如果成功，这个项目将引入一个有价值的工具，用于研究新兴的一类轨道相干材料，如石墨烯和拓扑绝缘体的显着动力学特征。 除了对研究生进行先进光学技术培训外，该项目还将努力增加代表性不足的科学家作为共用设备设施的导师的参与和知名度。非技术摘要 * 当电线连接到电池的两端时，电流就会流动，这对大多数人来说并不奇怪。 中学的物理课程告诉学生，当磁铁在一个封闭的电线环附近摆动时，电流就会在环中流动。 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池不能占据任意的构型。 如果熔池足够小，那么电子的量子力学波必须在绕熔池运动时平滑地与自身连接。 因此，即使外部磁体的相对位置和方向保持静止，熔池也会携带小的量子力学电流。 在这个项目中，PI将引入一种全新类型的激光光谱学，激发固体中的量子力学电流并监测它们的时间演化。 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。 除了对研究生进行先进光学技术培训外，该项目还将增加代表性不足的科学家作为共享设备设施中的导师的参与度和知名度。

****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.