(a) Electron spin resonance in NV spins driven by spin waves demonstrated by Andrich et al. [10]. An array of nanodiamonds is patterned inside a PDMS film layered on top of a YIG thin film. From a distant MSL deposited on the YIG the antenna field propagates through the PDMS and couples to the NV centers. Inside the YIG the microwave excitation by the MSL leads to spin waves propagating in the plane. Due to the given dimensions, the theoretical treatment can be reduced to a two-dimensional coordinate system as shown in (b), which is a cross section of the setup in (a). The layered structure lies in the x plane and the center of the MSL of width w marks the origin of the coordinate system and is oriented along the y direction.

Project B06: Phys. Rev. B 2019

Magnetic resonance in defect spins mediated by spin waves

In search of two level quantum systems that implement a qubit, the nitrogen-vacancy (NV) center in diamond has been intensively studied for years. Despite favorable properties such as remarkable defect spin coherence times, the addressability of NV centers raises some technical issues. The coupling of a single NV center to an external driving field is limited to short distances, since an efficient coupling requires the NV to be separated by only a few microns away from the source. As a way to overcome this problem, an enhancement of coherent coupling between NV centers and a microwave field has recently been experimentally demonstrated using spin waves propagating in an adjacent yttrium iron garnet (YIG) film [P. Andrich et al., npj Quantum Inf. 3, 28 (2017)]. In this paper we analyze the optically detected magnetic resonance spectra that arise when an NV center is placed on top of a YIG film for a geometry similar to the one in the experiment. We analytically calculate the oscillating magnetic field of the spin wave on top of the YIG surface to determine the coupling of spin waves to the NV center. We compare this coupling to the case when the spin waves are absent and the NV center is driven only with the antenna field and show that the calculated coupling enhancement is dramatic and agrees well with the one obtained in the recent experiment.

C. Mühlherr, V. O. Shkolnikov, G. Burkard
Physical Review B 99, 195413 (2019)
DOI: 10.1103/PhysRevB.99.195413