Imaging Quantum Materials with Scanning Quantum magnetometry

In recent years, there has been rapid growth in the ability to isolate and control atomic quantum systems. While
they are most famous for their potential use for quantum computation, the atoms’ high coherence and controllability
also make them ideal sensors. The nitrogen-vacancy (NV) center is an isolated quantum spin defect in diamond, of
atomic size and with extreme (∼ 1 nT) sensitivity to magnetic field [1]. To make a robust probe which utilizes the
nanscale spatial resolution of the NV center, the diamond is shaped into a pillar with the sensor at its tip. This tip
can be brought into atomic contact with the measured material and scan across it [2].
Notably, NV sensors are capable to operate across a wide temperature range (10 mK − 1000 K), which is very
unique amongst its contemporaries. In addition, one can easily detect both static magnetic fields (commonly used
approach) [3, 4] as well as any magnetic field fluctuations or magnetic noise up to GHz frequency [5–8] using NV
magnetometry technique. The latter approach is particularly suitable for directly imaging current distributions,
complex spin textures or their interactions at the nanoscale, an information that is often missing in conventional
non-local transport measurements.

However, operating an NV magnetometry setup requires expertise in cryogenics, scanning probe approaches, optics,
high frequency operations (GHz range), and coherent quantum control, and only very recently such systems have
become operational and are starting to show initial results. With these novel experimental capabilities, we are now
ready to explore a wide variety of quantum materials and discover new physical effects. This PhD project will be jointly
supervised by two PIs at TU Dresden and the MPI-CPfS, offering a unique scope to operate and to gain expertise on
NV magnetometry in extreme conditions. The Nanoscale Quantum Materials (Singha) group has developed a homebuilt
NV magnetometry setup that operates at 4 K under ultra high vacuum condition and allows sample preparations
in a surface sensitive manner [9, 10], whereas the Quantum Information for Quantum Materials (Vool) group operates
room temperature and variable temperature (1.8-200 K) NV magnetometry setups with high magnetic field (up to 5
T). In this PhD project, you will explore and understand novel quantum materials by probing their local magentic
signatures using NV magnetometry under variable experimental conditions.