Lonsdaleite Defects Promise Novel Quantum Sensors

Computational modelling reveals three configurations of nitrogen-vacancy (NV) colour centres within hexagonal diamond (lonsdaleite), one unique to its structure. These NV centres, created by carbon lattice defects, exhibit distinct thermochemical stability, photophysical properties and magneto-optical characteristics. Predicted ground state fine structure splitting differs from cubic diamond – 2.74 GHz and 4.56 MHz – offering a definitive spectroscopic signature for hexagonal diamond. Optically detected magnetic resonance utilising these centres provides both a novel carbon-based quantum system and a method to confirm lonsdaleite’s hexagonal structure.

The search for materials exhibiting exceptional hardness and unique electronic properties continues to drive materials science. Recent computational work focuses on lonsdaleite, a hexagonal allotrope of carbon theorised to surpass conventional diamond in hardness and possess a wider bandgap – a key characteristic influencing its potential in various applications. This altered structure is predicted to host ‘colour centres’, defects within the crystal lattice that exhibit sensitivity to external stimuli. A team led by Anjay Manian (abc), Mitchell O. de Vries, Daniel Stavrevski, and Qiang Sun (d), with contributions from Salvy P. Russo (a) and Andrew D. Greentree (d f), present detailed ab initio modelling of nitrogen-vacancy (NV) colour centres within lonsdaleite nanocrystals.

Their research, detailed in the article “Nitrogen-vacancy centre in lonsdaleite: a novel nanoscale sensor?”, identifies distinct NV configurations unique to the hexagonal structure, potentially offering an unambiguous method for confirming lonsdaleite’s hexagonal nature and opening avenues for novel nanoscale sensing technologies.

The investigation of hexagonal diamond, also known as lonsdaleite, reveals distinct nitrogen-vacancy (NV) colour centres within nanocrystals, differing from those observed in conventional cubic diamond. Researchers perform ab initio calculations to characterise both neutral (NV⁰) and negatively charged (NV⁻) defects, identifying three configurations for the NV⁰ centre and establishing a foundation for understanding their unique properties. Two of these configurations closely resemble NV centres found in cubic diamond, residing on a single carbon plane, while a unique configuration exists exclusively within the hexagonal lattice, where the nitrogen and vacancy each coordinate to four neighbouring carbon atoms.

This unique configuration presents a definitive spectroscopic signature for identifying lonsdaleite, distinguishing it from other carbon allotropes and offering a pathway for unambiguous material characterization. Calculations demonstrate that all modelled NV derivatives exhibit thermodynamic stability, possessing unique photophysical properties, spectral profiles, and magneto-optical characteristics, which are crucial for potential applications in quantum technologies. By extrapolating from known cubic diamond NV properties, the team predicts ground state fine structure splitting of 2.74 GHz and 4.56 MHz for two of the hexagonal diamond NV centres, differing slightly from the 2.87 GHz observed in cubic diamond and providing a measurable parameter for experimental verification.

Computational modelling reveals distinct nitrogen-vacancy (NV) colour centres within hexagonal diamond (lonsdaleite) nanocrystals, differing from those observed in conventional cubic diamond, and establishing a basis for exploring their potential in quantum applications. Researchers perform ab initio calculations to characterise both neutral (NV⁰) and negatively charged (NV⁻) defects, identifying three configurations for the NV⁰ centre and providing insights into their structural arrangements. Two of these configurations closely resemble NV centres found in cubic diamond, residing on a single carbon plane, while a unique configuration exists exclusively within the hexagonal lattice, where the nitrogen and vacancy each coordinate to four neighbouring carbon atoms.

This unique configuration presents a definitive spectroscopic signature for identifying lonsdaleite, distinguishing it from other carbon allotropes and offering a clear pathway for unambiguous material characterization. The calculations demonstrate that all modelled NV derivatives exhibit thermodynamic stability, possessing unique photophysical properties, spectral profiles, and magneto-optical characteristics, which are crucial for potential applications in quantum technologies. By extrapolating from known cubic diamond NV properties, the team predicts ground state fine structure splitting of 2.74 GHz and 4.56 MHz for two of the hexagonal diamond NV centres, differing slightly from the 2.87 GHz observed in cubic diamond and providing a measurable parameter for experimental verification.

Hexagonal diamond, also known as lonsdaleite, represents a fascinating allotrope of carbon predicted to surpass cubic diamond in hardness and exhibit a wider bandgap, making it a promising material for advanced technologies. Researchers anticipate the presence of sub-bandgap defect centers, or color centers, within its structure due to its purely sp bonded lattice, and perform ab initio modeling of nitrogen-vacancy (NV) color centers in hexagonal diamond nanocrystals, investigating both the neutral (NV⁰) and negatively charged (NV⁻) species. Calculations reveal three distinct configurations for the NV center: two mirroring NV centers found in cubic diamond, and a unique configuration exclusive to the hexagonal form, providing a foundation for understanding their unique properties.

This unique configuration presents a definitive spectroscopic signature for identifying lonsdaleite, distinguishing it from other carbon allotropes and offering a clear pathway for unambiguous material characterization. Calculations demonstrate that all identified derivatives exhibit thermochemical stability, each possessing unique photophysical properties, spectral profiles, and magneto-optical characteristics, which are crucial for potential applications in quantum technologies. By assuming ground state properties comparable to those of NV in cubic diamond, albeit with increased strain, researchers predict ground state fine structure splitting for two of the hexagonal NV centers to be 2.74 GHz and 4.56 MHz, compared to 2.87 GHz for cubic diamond, providing a measurable parameter for experimental verification.

The diamond-like NV systems consist of three symmetry-equivalent centers residing on the same carbon plane, alongside a defect that bridges two planes by replacing a carbon-carbon bond, and researchers also identify an additional NV center where both the nitrogen and vacancy possess four nearest neighbor carbon atoms. The existence of this latter configuration serves as definitive proof of the hexagonal nature of lonsdaleite, providing a clear pathway for unambiguous material characterization. Through chemical analysis, researchers demonstrate that all identified derivatives exhibit thermochemical stability, each possessing unique photophysical properties, spectral profiles, and magneto-optical characteristics, which are crucial for potential applications in quantum technologies.

Researchers predict ground state fine structure splitting for two of the hexagonal NV centers to be 2.74 GHz and 4.56 MHz, compared to 2.87 GHz for cubic diamond, providing a measurable parameter for experimental verification. The potential for optically detected magnetic resonance utilizing NV centers in lonsdaleite introduces a novel carbon-based system and provides an unambiguous pathway for material characterization. Researchers anticipate that these findings will pave the way for the development of advanced quantum technologies based on hexagonal diamond, offering improved performance and functionality.

Researchers perform ab initio calculations to characterise both neutral (NV⁰) and negatively charged (NV⁻) defects, identifying three configurations for the NV⁰ centre and establishing a foundation for understanding their unique properties. Two of these configurations closely resemble NV centres found in cubic diamond, residing on a single carbon plane, while a unique configuration exists exclusively within the hexagonal lattice, where the nitrogen and vacancy each coordinate to four neighbouring carbon atoms. This unique configuration presents a definitive spectroscopic signature for identifying lonsdaleite, distinguishing it from other carbon allotropes and offering a clear pathway for unambiguous material characterization.

Calculations demonstrate that all modelled NV derivatives exhibit thermodynamic stability, possessing unique photophysical properties, spectral profiles, and magneto-optical characteristics, which are crucial for potential applications in quantum technologies. By extrapolating from known cubic diamond NV properties, the team predicts ground state fine structure splitting of 2.74 GHz and 4.56 MHz for two of the hexagonal diamond NV centres, differing slightly from the 2.87 GHz observed in cubic diamond and providing a measurable parameter for experimental verification. Researchers anticipate that these findings will pave the way for developing advanced quantum technologies based on hexagonal diamond, offering improved performance and functionality.