Scanning Nitrogen-Vacancy Centre Magnetometer

量子力学系统天生对外部扰动高度敏感。这使它们成为传感器应用的理想候选者。量子传感器在测量物理性质（如电磁场）、热力学性质（如温度）和机械性质（如旋转）的新技术的发展中获得了极大的兴趣。与传统的基于经典物理的传感技术相比，量子传感器的主要优点是精度高。在这里，我们提出使用扫描氮空位（NV）中心显微镜来感应磁场，具有超高的时空分辨率。扫描磁强计结合了光学共聚焦显微镜和原子力显微镜。金刚石原子力显微镜尖端的单个带负电荷的NV缺陷被用作测量磁场的原子大小的传感器。为此，NV中心的量子自旋态被光学初始化，并以良好的表征方式与磁场相互作用。由此产生的自旋状态是用光学检测的磁共振光谱读出的。这允许在环境条件下精确定量地测定磁场，易于检测5-10µT的磁场。通过扫描样品表面的尖端，扫描NV磁力计同时记录样品地形图和存在于表面的磁场，空间分辨率低至~10 nm。除了用于测量直流磁场的连续光学和微波泵浦外，使用已建立的光学和微波脉冲序列的脉冲测量允许更高的磁场灵敏度低至0.5-1µT，以及高达GHz频段的时间分辨率。NV中心的长且与环境相关的相干时间可以通过自旋弛豫测量实现噪声光谱。传统的纳米级磁化成像技术，如自旋极化扫描隧道显微镜和x射线光谱学，需要专门的样品制备和复杂的实验装置。磁力显微镜等替代技术是基于感应杂散场。然而，这些技术大多是微扰的，不容易量化。扫描NV显微镜的主要优点是它们与不同样品和环境的广泛兼容性，以及测量的非摄动性质。我们的提案团队在分子自旋电子学，新型磁性材料和NV磁强计方面具有不同的专业背景。我们建议利用高度通用的扫描NV磁力计装置的独特功能，用于广泛的研究项目，从成像磁性材料中的自旋织构结合磁输运测量到检测分子中的核磁共振。

Quantum mechanical systems are inherently highly sensitive to external disturbances. This makes them ideal candidates for applications as sensors. Quantum sensors have gained significant interest in the development of novel technologies for measuring physical properties such as electromagnetic fields, thermodynamic properties such as temperature, and mechanical properties such as rotation. Compared to conventional sensing techniques based on classical physics, the key benefit of quantum sensors is their high precision. Here, we propose using a scanning nitrogen-vacancy (NV) centre microscope for sensing magnetic fields with ultra-high spatial and temporal resolution. A scanning NV magnetometer combines an optical confocal microscope with an atomic force microscope. A single negatively charged NV defect at the apex of a diamond atomic force microscopy tip is used as an atomic-sized sensor for measuring magnetic fields. For this, the quantum spin state of the NV centre is initialised optically and interacts with the magnetic field in a well-characterised manner. The resulting spin state is read out using optically detected magnetic resonance spectroscopy. This allows for precise and quantitative determination of the magnetic fields under ambient conditions with an easily detectable field of 5-10 µT. By scanning the sharp tip across the sample surface, the scanning NV magnetometer simultaneously records a map of the sample topography and the magnetic field present at the surface with a spatial resolution of down to ~10 nm. In addition to continuous optical and microwave pumping for measuring DC magnetic fields, pulsed measurement using established sequences of optical and microwave pulses allow for higher magnetic field sensitivity down to 0.5-1 µT as well as temporal resolution up to the GHz regime. NV centres' long and environment-dependent coherence times enable noise spectroscopy via spin relaxometry. Conventionally used techniques to image magnetization on the nanoscale such as spin-polarised scanning tunnelling microscopy and X-ray spectroscopy require dedicated sample preparation and complex experimental setups. Alternative techniques such as magnetic force microscopy are based on sensing stray fields. However, most of these techniques are perturbative and are not easily quantifiable. The key benefits of scanning NV microscopes are their wide compatibility with different samples and environments, and the non-perturbative nature of the measurement. Our proposal team has a diverse background with expertise in molecular spintronics, novel magnetic materials and NV magnetometry. We propose to make use of the unique features of the highly versatile scanning NV magnetometer setup for a wide spectrum of research projects ranging from imaging spin textures in magnetic materials in combination with magneto-transport measurements to detecting nuclear magnetic resonance in molecules.