Ground State Of Defect Research Articles

Room temperature optically detected magnetic resonance of single spins in GaN.

High-contrast optically detected magnetic resonance is a valuable property for reading out the spin of isolated defect colour centres at room temperature. Spin-active single defect centres have been studied in wide bandgap materials including diamond, SiC and hexagonal boron nitride, each with associated advantages for applications. We report the discovery of optically detected magnetic resonance in two distinct species of bright, isolated defect centres hosted in GaN. In one group, we find negative optically detected magnetic resonance of a few percent associated with a metastable electronic state, whereas in the other, we find positive optically detected magnetic resonance of up to 30% associated with the ground and optically excited electronic states. We examine the spin symmetry axis of each defect species and establish coherent control over a single defect's ground-state spin. Given the maturity of the semiconductor host, these results are promising for scalable and integrated quantum sensing applications.

Quantum metrology with a single spin- 32 defect in silicon carbide

We show that implementations for quantum sensing with exceptional sensitivity and spatial resolution can be made using spin-3/2 semiconductor defect states. We illustrate this using the silicon monovacancy deep center in hexagonal SiC based on our rigorous derivation of this defect's ground state and of its electronic and optical properties. For a single $\textrm{V}_{\textrm{Si}}^-$ defect, we obtain magnetic field sensitivities capable of detecting individual nuclear magnetic moments. We also show that its zero-field splitting has an exceptional strain and temperature sensitivity within the technologically desirable near-infrared window of biological systems. The concepts and sensing schemes developed here are applicable to other point defects with half spin multiplet ($S\geq 3/2$) configuration.

Optical determination of the spatial extent of defects in insulators

We have studied the size of common electron-excess defects using the Vinti sum rule that relates the mean-square radius of a defect's ground state to its optical absorption spectrum. Here we present the single-electron sum-rule theory and consider its many-electron extension. We show that numerous electron-excess defects in highly ionic systems, including F centers and substitutional s 2 impurity anions, are highly localized, primarily to a single lattice site. Similar defects in alkaline-earth oxides and sulfides are more diffuse, presumably because of greater covalent mixing between quantum states of the defect and the host.