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 in an isolated quantum spin trapped in a diamond, of atomic size and with extreme (∼ 1 nT) sensitivity to magnetic field. This unique sensor allows us to explore and visualize a wide range of effects in quantum materials, such as magnetization structure [1, 2], correlated electron current flow profile [3], and electromagnetic noise [4].
To make a robust scanning probe which utilizes the nanscale spatial resolution of the NV probe, the diamond is shaped into a pillar with the NV center at its tip. This tip can be brought into atomic contact with the measured material and scan across it [5]. Furthermore, the NV sensor is unique its ability to operate in a wide temperature range (10 mK − 1000 K). Making use of this ability, however, requires a variable-temperature cryostat for scanning magnetometry [3]. Operating such a setup requires expertise in cryogenics, scanning, optics, microwave, 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.
In this PhD project, you will help set up and operate a new variable-temperature cryogenic NV scanning probe and use it to explore and understand quantum materials through their local magnetic signatures. Utilizing the expertise at the MPI-CPfS in creating state-of-the-art quantum materials and devices, this quantum probe will allow us to visualize their internal structure and gain insight into their underlying physics.

(a) NV scanning probe: a diamond pillar with a single spin at its tip. (b) Electric current profile vs. temperature, showing electron hydrodynamic flow. Reproduced from [3].

References

[1] L. Thiel, Z. Wang, M. A. Tschudin, D. Rohner, I. Gutirrez-Lezama, N. Ubrig, M. Gibertini, E. Giannini, A. F. Morpurgo, and P. Maletinsky
Probing magnetism in 2D materials at the nanoscale with single-spin microscopy
Science 364 (6444), 973-976 (2019)
[2] Q.-C. Sun, T. Song, E. Anderson, A. Brunner, J. Förster, T. Shalomayeva, T. Taniguchi, K. Watanabe, J. Gräfe, R. Stöhr, X. Xu, and J. Wrachtrup
Magnetic domains and domain wall pinning in atomically thin CrBr3 revealed by nanoscale imaging
Nat Commun 12, 1989 (2021)
[3] U. Vool, A. Hamo, G. Varnavides, Y. Wang, T. X. Zhou, N. Kumar, Y. Dovzhenko, Z. Qiu, C. A. C. Garcia, A. T. Pierce, J. Gooth, P. Anikeeva, C. Felser, P. Narang, A. Yacoby
Imaging phonon-mediated hydrodynamic flow in WTe2 with cryogenic quantum magnetometry
Nature Physics (2021)
[4] S. Kolkowitz, A. Safira, A.A. High, R. C. Devlin, S. Choi, Q.P. Unterreithmeier, D. Patterson, A.S. Zibrov, V.E. Manucharyan, H. Park, and M.D. Lukin
Probing Johnson noise and ballistic transport in normal metals with a single-spin qubit
Science 347, 1129 (2015)
[5] P. Maletinsky, S. Hong, M. S. Grinolds, B. Hausmann, M. D. Lukin, R. L. Walsworth, M. Loncar, and A. Yacoby
A robust scanning diamond sensor for nanoscale imaging with single nitrogen-vacancy centres
Nature Nanotechnology 7, 320 (2012)

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