All-optical dc nanotesla magnetometry using silicon vacancy fine structure in isotopically purified silicon carbide

TL;DR

This paper demonstrates a highly sensitive, all-optical dc magnetometry technique using silicon vacancy centers in isotopically purified silicon carbide, achieving nanotesla sensitivity at room temperature without radiofrequency fields.

Contribution

The study uncovers the fine structure of silicon vacancies in isotopically purified silicon carbide and utilizes it for contactless, all-optical magnetic field sensing with high sensitivity and temperature robustness.

Findings

Achieved dc magnetic field sensitivity of 87 nT/Hz^{1/2} at room temperature.

Demonstrated robustness of the method up to 500 K.

Projected sensitivity below 100 fT/Hz^{1/2} with optimized waveguide.

Abstract

We uncover the fine structure of a silicon vacancy in isotopically purified silicon carbide (4H-$^{28}$SiC) and find extra terms in the spin Hamiltonian, originated from the trigonal pyramidal symmetry of this spin-3/2 color center. These terms give rise to additional spin transitions, which are otherwise forbidden, and lead to a level anticrossing in an external magnetic field. We observe a sharp variation of the photoluminescence intensity in the vicinity of this level anticrossing, which can be used for a purely all-optical sensing of the magnetic field. We achieve dc magnetic field sensitivity of 87 nT Hz$^{-1/2}$ within a volume of $3 \times 10^{-7}$ mm$^{3}$ at room temperature and demonstrate that this contactless method is robust at high temperatures up to at least 500 K. As our approach does not require application of radiofrequency fields, it is scalable to much larger volumes. For an optimized light-trapping waveguide of 3 mm$^{3}$ the projection noise limit is below 100 fT Hz$^{-1/2}$.