Magnetic Nanoscopy with Diamond NV Centers

提出了一种利用金刚石中氮空位(NV)色心的薄层进行纳米尺度磁场成像的新方法，并将其与亚光波长探测技术相结合。到目前为止，单NV中心的磁场传感已经显示出5nT/Hz1/2的灵敏度。这已经足以检测到50 nm处的单个电子自旋或5 nm处的单个核自旋。同时，NV中心的尺寸估计为0.3 nm。在这个距离刻度上，没有其他磁传感器具有这样的灵敏度。使用扫描探头技术，用NV中心制作了纳米尺度的磁场图像，并展示了微尺度的全帧成像。亚波长受激发射耗尽显微镜也使用了单个NV中心，即使在低强度的甜甜圈光束下也获得了高于10 nm的分辨率。方法是使用系综来消除在感兴趣的对象附近控制纳米精度的扫描探头的需要，同时使用耗尽显微镜来保持空间分辨率。然而，为了实现这一势，人们必须首先更好地理解NV系综的物理，特别是它们的磁灵敏度如何依赖于NV浓度以及与用于受激发射耗尽(STED)和基态耗尽显微镜(GSD)的激光的相互作用。该项目将建立在伯克利和德克萨斯农工集团可用的综合专业知识和基础设施的基础上。该项目的顶端将是对与生物相关的系统-三角扇贝-一种以其在地球磁场中导航的能力而闻名的100 nm直径磁链的磁性纳米显微镜。智力优势：拟议的研究将导致空间分辨总体磁学的NV-钻石集合的优化，阐明NV-中心的基本物理(包括确定磁共振参数的温度依赖性等)，了解STED/GSD泵浦光束对灵敏度的影响，并在此基础上开发优化的磁测量方法。预期的纳米级传感器将具有足够的灵敏度，可以看到材料中的纳米级磁区。广泛的影响将是提供一种没有移动部件的磁共振作用力显微镜的替代方法。由于主机的极高化学稳定性和远程光学检测协议，NV中心也可用于微流控“单芯片实验室”系统，允许对微量分析物进行化学分析和成像。这是工业、安全和医学中的一个重要应用，因为它允许快速和通用地识别危险物质。一个关键的应用领域是生物系统的磁成像，这将通过对Tritonia diomedea的磁链的测量来证明。钻石色心的研究具有广泛的教育影响，因为NV中心的简单几何形状是理解量子力学和固态物理更广泛概念的便捷教学工具。NV合奏只需一支激光笔和一块磁铁就可以向学生演示磁感应的原理。让K-12学生亲自动手进行磁感应，再加上钻石的社会神秘性，也可以作为女性等代表性不足群体的一种新的招聘工具。本科生的参与，特别是通过伯克利大学的本科生-研究-学徒计划和TAMU的实验光学课程，是计划的。

A novel approach to nanoscale magnetic-field imaging using a thin layer of nitrogen-vacancy (NV) color centers in diamond and combining this with sub-optical-wavelength probing techniques is proposed. Magnetic-field sensing with single NV centers so far has shown a sensitivity of 5 nT/Hz1/2. Already this is sufficient to detect a single electron spin at 50 nm distances or a single nuclear spin at 5 nm. At the same time, the NV center is estimated at 0.3 nm in size. No other magnetic sensor has this sensitivity on this distance scale. Nanoscale magnetic field images have been made with NV centers using scanning-probe techniques, and microscale full-frame imaging with ensembles has been demonstrated. Sub-wavelength stimulated emission depletion microscopy has also been done using single NV centers and achieved better than 10 nm resolution even with low-intensity donut beams. The approach is to use ensembles to eliminate the need to control a scanning probe with nanometer precision near the object of interest while using depletion microscopy to maintain the spatial resolution. However, to realize this potential one must first better understand the physics of NV ensembles, especially how their magnetic sensitivity depends on NV concentration and interactions with the lasers used in the stimulated-emission-depletion (STED) and ground-state-depletion microscopy (GSD). The project will build on the combined expertise and infrastructure available to the Berkeley and Texas A&M groups. The apex of the project will be magnetic nanoscopy of a biologically relevant system---100 nm diameter magnetic chains in Tritonia diomedea---a sea slug known for its ability to navigate in the Earth's magnetic field.Intellectual merit: The proposed studies will lead to optimization of the NV-diamond ensembles for spatially-resolved ensemble magnetometry, elucidation of the fundamental physics of the NV-centers (including determination of temperature dependence of the magnetic-resonance parameters, etc.), understanding of the effect of the STED/GSD pump beam on sensitivity, and development of optimized magnetometry methodology based on this knowledge. The anticipated nanoscale sensor will have enough sensitivity to see nanoscale magnetic domains in materials. Broad impact will be to provide an alternative to magnetic resonance force microscopy with no moving parts. Due to extreme chemical stability of the host and the remote optical detection protocol, NV centers can also be used in microfluidic ``lab-on-a-chip'' systems, allowing chemical analysis and imaging with minute quantities of analytes. This is an important application in industry, security, and medicine, as it allows rapid and universal identification of dangerous substances. A key area of application is magnetic imaging of biological systems which will be demonstrated by measurements on magnetic chains in Tritonia diomedea. The study of color centers in diamond has broad educational impact, as the simple geometry of the NV center is a convenient teaching tool for understanding the broader concepts of quantum mechanics and solid-state physics. NV ensembles can demonstrate the principles of magnetic sensing to students using only a laser pointer and a magnet. Letting K-12 students perform hands-on magnetic sensing, combined with the social mystic of diamonds can also be used as a novel recruiting tool for underrepresented groups such as women. Involvement of undergraduates, specifically through the Berkeley undergraduate-research-apprenticeship program and TAMU's experimental optics course, is planned.