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。 这些器件的应用包括成像、光通信和可再生能源。提高它们的性能依赖于理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。该团队将对材料内部的光电流进行空间成像，并确定纳米级变化如何影响其产生和传输。 这些测量将由一种非侵入式传感器进行，该传感器利用金刚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，以感测由这种光电流产生的弱磁场。首席研究员将创建动手演示和视频，以激发对量子现象的好奇心。这些活动将培养学生，包括代表性不足群体的学生，在科学和技术领域接受教育和从事科学和技术职业的内在动力。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学测量，称为扫描光电流显微镜，提供光电流产生的强大真实空间视图;然而，材料内部光载流子的实际路径被隐藏。这种缺失的观点对于澄清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生载流子的散射和弛豫非常重要。为了解决这一挑战，本项目开发了空间分辨磁力测量法，使用金刚石中氮空位中心的电子自旋。基于共焦显微镜，该技术很容易集成光激发和光学读出传感器自旋映射杂散磁场从光电流流动。这些磁场图被用来提取的振幅和方向的光电流在二维材料和薄的散装样品。通过同步脉冲光激发与量子传感器自旋的相干操纵来实现高灵敏度，而通过扫描基于金刚石的原子力显微镜探针来实现高空间分辨率。对拓扑结构、对称性和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的光电探测器的发展。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响评审标准进行评估，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.