Discovery of ST2 centers in natural and CVD diamond

TL;DR

This paper reports the discovery and characterization of the ST2 defect center in diamond, highlighting its potential for quantum sensing due to its wide magnetic field acceptance angle and optically addressable spin states.

Contribution

The study introduces the ST2 center in natural and artificially created diamonds, maps its optical and electronic properties, and demonstrates its promising sensing capabilities.

Findings

ST2 centers are optically addressable and have multiple orientations.

ST2 exhibits a wide acceptance angle for magnetic field sensing.

The chemical structure of ST2 remains unknown.

Abstract

The ST2 center is an optically addressable point defect in diamond that facilitates spin initialization and readout. However, while this study presents the discovery of ST2 centers first observed in a natural diamond and provides a reliable technique for artificially creating them, its chemical structure remains unknown. To assess the potential of ST2, we map out its basic optical characteristics, reveal its electronic level structure, and quantify the intrinsic transition rates. Furthermore, we investigate its response to microwaves, static magnetic fields, and the polarization of excitation laser light, revealing twelve inequivalent orientations of the ST2 center. Simultaneous exposure to microwaves and static magnetic fields also reveals an exceptionally wide acceptance angle for sensing strong magnetic fields, unlike the well-established NV center, which is sensitive only within a narrow cone aligned with its symmetry axis. This finding establishes the ST2 center as a highly promising candidate for nanoscale quantum sensing.