报告摘要: The nitrogen-vacancy (NV) center is a point defect where one carbon atom in the diamond’s crystal lattice is replaced by a nitrogen atom and an adjacent lattice site is left empty. It is an atom-like system with well-defined spin properties. These spin properties make it a promising nanoscale quantum sensor for the magnetic field with an operating temperature range from cryogenic to above room temperature and a dynamic range spanning from DC to GHz. Scanning NV magnetometry, which uses a single NV center as a scanning sensor, has been demonstrated as a powerful tool in high-resolution, high-sensitivity magnetic field imaging at room temperature. However, its cryogenic application remains challenging. I this talk, I will introduce our recently developed cryogenic scanning NV magnetometry at the University of Stuttgart. With this technique, we directly observed magnetic domains and moiré magnetism in van der Waals magnetic materials, which cannot be realized with conventional magnetic imaging techniques.