Quantum spin dynamics; sensing, control, and imaging

AN Laboratory
Associate Professor：AN, Toshu

E-mail：
［Research areas］
nano spin science, spintronics, nano MRI
［Keywords］
quantum sensing, diamond NV center, magnetic resonance imaging, spin waves, scanning probe microscopy, laser confocal microscopy

Skills and background we are looking for in prospective students　

Basic knowledge of physics, condensed matter physics, and electrical engineering. Diligence to master a skill, and will to challenge to new things.

What you can expect to learn in this laboratory

The objective of this laboratory is detection, control and imaging of spin dynamics at nanoscale. Spin physics such as magnetic resonance, and spin current based on quantum mechanics are explored, in ferromagnetic, antiferromagnetic, and paramagnetic materials, at nanoscale. For nanoscale spin sensing, nitrogen vacancy (NV) center in diamond is used, and combined with confocal microscope and atomic force microscope. Technical skills of electrical engineering for microwaves, optics, and scanning probe microscope are developed.

【Job category of graduates】
Manufacturing, analyzing, and development and research work of electronics and materials related companies

Research outline

We focus on study of sensing "spin dynamics" in magnetic materials and its control at nanoscale. We explore novel phenomena related to spin dynamics and extract fundamental physics behind for the application to the spin device and the magnetic sensor device. For this purpose, highly sensitive and high-resolution spatial magnetic sensing and imaging methods are developed (Fig. 1).

Fig. 1, Spins in electron and nuclei, spin resonance and spin current

(1) Nanoscale magnetic field sensing using nitrogen-vacancy center in diamond

Recently, nitrogen vacancy center (NV center) in diamond crystal is attracting much attention for utilizing it as a spin sensor (Fig. 2), since spin state existing in a combination of a carbon defect and nitrogen indiamond named as nitrogen-vacancy center (NV center) was demonstrated to be detected through fluorescence measurement (Gruber and Wrachtup, et al., Science, 276, 2012 (1997)).
Interestingly, this optically detected magnetic resonance (ODMR) can be used for sensing spins existing around (Fig. 3). Especially, making a NV center as a scanning spin imaging probe (Fig. 4).

Fig. 2, NV center in diamond, and its magnetic resonance signal

(2) Long-distance excitation of NV center via surface spin waves

We succeeded to excite NV center by spin waves; collective emotion of spins excited from 3.6 millimeter distance [1]. This will be new system to study interactions of spins.

Fig. 3, spin conversion from spin wave to NV center

(3) Development of scanning NV center spin sensing probe

Fig. 4, scanning NV center spin sensing probe combined with AFM

Key publications

1. Yuta Kainuma, Kunitaka Hayashi, Chiyaka Tachioka, Mayumi Ito, Toshiharu Makino, Norikazu Mizuochi, and Toshu An "Scanning diamond NV center magnetometer probe fabricated by laser cutting and focused ion beam milling" Journal of Applied Physics 130, 243903 (2021)
2. Dwi Prananto, Yuta Kainuma, Kunitaka Hayashi, Norikazu Mizuochi, Ken-ichi Uchida, and　 Toshu An "Probing Thermal Magnon Current Mediated by Coherent Magnon via Nitrogen-Vacancy Centers in Diamond" Phys. Rev. Applied 16, 064058 (2021).
3. D. Kikuchi, D. Prananto, K. Hayashi, A. Laraoui, N. Mizuochi, M. Hatano, E. Saitoh, Y. Kim, C. A. Meriles, T. An, Long-distance excitation of nitrogen-vacancy centers in diamond via surface spin waves, Applied Physics Express, 10, 103004 1-4 (2017)

Equipment

Home-made diamond NV center-based spin sensing apparatus, based on confocal microscopy, and atomic force microscopy.