Seminar "Microwave engineering, magnetic sensing technique, and materials science for nitrogen-vacancy centers in diamond" by Dr. Eisuke Abe

Speaker: Dr. Eisuke Abe, Project Lecturer, Spintoronics Research Center, Keio University

Title: Microwave engineering, magnetic sensing technique, and materials science for nitrogen-vacancy centers in diamond

Abstract:

Electronic spins of nitrogen-vacancy (NV) centers in diamond possess long coherence times, and are individually addressable using optical and microwave techniques. The NV spins are thus promising candidates for ultra-sensitive high-spatial-resolution magnetometers as well as quantum memories for quantum communication. Aiming for such wide and ambitious applications, the research on the NV centers is highly interdisciplinary, and various facets of science and technology must be considered and combined together.

In this seminar, I will report on our group’s recent efforts to better control and utilize the NV spins, emphasizing our microwave engineering, spin physics, and materials science approaches. First I will introduce a circular microwave resonator designed to create microwaves with arbitrary polarizations with its resonance frequency dynamically tunable between 2 and 3.2 GHz [1]. Such polarization- and frequency-controlled microwaves enable the near-perfect selective excitation of the NV spins. I will then discuss the spin physics of high-density (10¹⁷ cm⁻³) and narrow resonance-linewidth (200 kHz) NV ensemble created with a combination of CVD growth of 100-nm thick ¹²C diamond and He⁺ ion implantation [2]. Decoherence spectroscopy reveals an interaction between the NV spins and other electron spins, identified as substitutional nitrogen donor spins, and thereby demonstrates magnetic sensing on electron spins [3]. The average distance between the NV spin and the donor spin is about 20 nm, suggesting that an NV spin positioned at a few nm deep from the diamond surface can detect external nuclear spins placed on the surface. To this end, our group is not only making a continuing effort to find CVD growth conditions optimized for creating shallow single NV centers [4], but also developing a new technique to create shallow NV centers using N⁺ ion implantation [5].

References

1. J. Herrmann et al., ‘Polarization- and frequency-tunable microwave circuit for selective excitation of nitrogen-vacancy spins in diamond’ Appl. Phys. Lett. 109, 183111 (2016).
2. E. E. Kleinsasser et al., ‘High density nitrogen-vacancy sensing surface created via He+ ion implantation of ¹²C diamond’ Appl. Phys. Lett. 108, 202401 (2016).
3. K. Sasaki et al., ‘Magnetic field sensitivity and decoherence spectroscopy of an ensemble of narrow-linewidth nitrogen-vacancy centers close to a diamond surface’ arXiv:1612.00088.
4. K. Ohashi et al., ‘Negatively Charged Nitrogen-Vacancy Centers in a 5 nm Thin ¹²C Diamond Film’ Nano Lett. 13, 4733 (2013).
5. K. Ito et al., In preparation.