CAREER: Imaging Light-Matter Interactions in Quantum Materials with Nanoscale Quantum Sensors

光到电的转换，称为光电流，是光电探测器和太阳能电池等设备的基础。这些设备的应用包括成像、光通信和可再生能源。提高它们的性能依赖于了解有效产生这些光电流的新机制，以及这些电流如何在材料中传播。该团队将在空间上成像材料内部的光电流流动，并确定纳米级的变化如何影响其产生和传输。这些测量将由一种非侵入性传感器进行，该传感器使用钻石中原子级缺陷的量子特性。传感器将被放置在材料样品附近，以检测由这种光电流产生的弱磁场。首席研究员将制作动手演示和视频，以激发人们对量子现象的好奇心。这些活动将促进学生，包括来自代表人数不足的群体的学生，在科学和技术领域追求教育和职业的内在动机。课程将强调量子信息科学中的跨学科概念，包括材料研究、计算机科学和工程。基于扫描聚焦激光束的电测量，即扫描光电流显微镜，提供了强大的光电流产生的真实空间视图；然而，材料内部光载体的实际路径被隐藏。这一缺失的观点对于澄清块体和边界之间的区别以及理解局部电、磁和结构变化如何影响光载流子的散射和驰豫是很重要的。为了应对这一挑战，该项目开发了使用钻石中氮空位中心的电子自旋的空间分辨磁学。基于共聚焦显微镜，该技术很容易将光激励和传感器自旋的光学读出结合在一起，从光电流流动中映射杂散磁场。这些磁场图被用来提取二维材料和薄体样品中的光电流的幅度和方向。高灵敏度是通过同步脉冲光激发与量子传感器自旋的相干操作来实现的，而高空间分辨率则是通过扫描基于金刚石的原子力显微镜探针来实现的。这里追求的对拓扑、对称性和山谷极化的基本理解影响了光电探测器、新型信息处理设备和更高效率光伏的发展。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The conversion of light into electricity, known as photocurrent, is the basis for devices such as photodetectors and solar cells. Applications for these devices include imaging, optical communication, and renewable energy. Enhancing their performance relies on understanding new mechanisms to efficiently generate these photocurrents and how these currents travel within the material. The team will spatially image the flow of photocurrents inside materials and determine how nanoscale variations affect its generation and transport. These measurements will be made by a noninvasive sensor that uses the quantum properties of an atomic-scale defect in diamond. The sensor will be placed near the material samples to sense weak magnetic fields generated by such photocurrents. The principal investigator will create hands-on demonstrations and videos to stimulate curiosity in quantum phenomena. These activities will foster intrinsic motivations for students, including from under-represented groups, to pursue education and careers in science and technology. Coursework will emphasize interdisciplinary concepts in quantum information science that encompass materials research, computer science, and engineering.Electrical measurements based on scanning a focused laser beam, known as scanning photocurrent microscopy, provide powerful real-space views of photocurrent generation; however, the actual path travelled by the photocarriers in the interior of the material is concealed. This missing viewpoint is important to clarify the distinction between bulk and boundary, as well as to understand how local electric, magnetic, and structural variations affect the scattering and relaxation of photocarriers. To address this challenge, this project develops spatially-resolved magnetometry using the electronic spin of the nitrogen-vacancy center in diamond. Based on confocal microscopy, the technique readily integrates photoexcitation and optical readout of the sensor spin to map stray magnetic fields from photocurrent flow. These magnetic field maps are used to extract the amplitude and direction of photocurrent flow in two-dimensional materials and thin bulk samples. High sensitivity is achieved by synchronizing pulsed photoexcitation with coherent manipulation of the quantum sensor spin, while high spatial resolution is achieved by scanning a diamond-based atomic force microscope probe. The fundamental understanding of topology, symmetry, and valley polarization pursued here impacts the development of photodetectors, novel information processing devices, and higher efficiency photovoltaics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.