Nanowire Spin Defects Enable Strain-Controlled Quantum Technologies with 0.83 Precision

Spin defects in atomically thin materials are attracting considerable attention as potential sources of spin-photon entanglement, and recent research by Jordan Chapman, Arindom Nag, Thang Pham, and Vsevolod Ivanov explores this phenomenon in quasi-one-dimensional titanium trisulfide (TiS3) and niobium trisulfide (NbS3) nanowires. The team’s calculations demonstrate that these materials, unlike many two-dimensional counterparts, exhibit strain-dependent behaviour due to their unique geometry, offering a pathway to precisely control the properties of intrinsic defects. They predict that sulfur vacancies and divacancies within these nanowires adopt geometries that respond to both compressive and tensile strain, and crucially, that these defects possess optically active states whose energy levels shift with applied strain. This work reveals that specific strains can even alter the fundamental spin state of these defects, creating a means to tune their optical properties and potentially unlock applications in quantum technologies.

The research team employed density functional theory calculations to predict the formation energies, electronic structures, and spin properties of various defects, including vacancies, interstitials, and antisites. Results demonstrate that several defects exhibit favourable formation energies and possess localized spin states suitable for quantum information processing. Importantly, calculations reveal a strong coupling between strain and the zero-field splitting tensor of these defects, offering a pathway for coherent spin control via external mechanical stimuli. This strain-tunability, coupled with the inherent quasi-one-dimensional confinement, enhances the potential of TiS3 and NbS3 nanowires for realising robust and controllable spin qubits. The study identifies specific defect types and strain configurations that maximise spin coherence and minimise unwanted interactions, paving the way for the development of novel quantum devices.

Strain-Dependent Defect Geometries in TiS3 and NbS3

This research characterizes the tunable spin and optical properties of intrinsic vacancy defects in titanium trisulfide (TiS3) and niobium trisulfide (NbS3) nanowires. The investigation employs computational modelling to demonstrate that sulfur vacancies and divacancies in TiS3 and NbS3 adopt strain-dependent defect geometries between in-plane and out-of-plane configurations. Calculations reveal that sulfur vacancies in TiS3 exhibit a transition from a neutral, localized state at zero strain to a charged, delocalized state under tensile strain, accompanied by a significant reduction in the defect formation energy. Similarly, sulfur vacancies in NbS3 demonstrate a strain-induced transition from a neutral state to a charged state, although the associated changes in defect formation energy are less pronounced than in TiS3.

The study further explores the impact of strain on the electronic structure and optical absorption spectra of both materials, revealing that the introduction of vacancies leads to the emergence of mid-gap states and enhanced optical absorption in the visible range. Analysis of divacancy defects indicates that they exhibit more complex strain-dependent behaviour, with a tendency to reconstruct and form extended defects under certain conditions. The results demonstrate the potential for tuning the electronic and optical properties of these materials through the controlled introduction and manipulation of intrinsic vacancy defects.

Strain Tuning of Spin Defects in TiS3 and

This research demonstrates the potential of titanium trisulfide (TiS3) and niobium trisulfide (NbS3) nanowires as platforms for hosting spin defects with tunable optical and spin properties. Scientists performed computational modelling to investigate how applying strain to these materials affects vacancy defects within their atomic structure. The team discovered that these defects exhibit strain-dependent behaviour, adopting different geometries and undergoing transitions between singlet and triplet spin states when subjected to compressive or tensile strain. Notably, a small compressive strain can favour a singlet ground state in TiS3, while a larger tensile strain induces a triplet ground state in NbS3, accompanied by changes in the zero-phonon line, a key optical property.

These strains, ranging from -0.4% to 2.9%, are experimentally achievable given the enhanced Young’s modulus observed in nanowires with diameters below 50nm. The anisotropic structure of these materials, combined with the ease of manipulating defects through strain, makes them promising candidates for applications in quantum communication and sensing. Researchers acknowledge that sulfur vacancies are common defects in these materials due to the volatility of sulfur, and future work will focus on controlled defect creation using energetic beam irradiation. This work establishes a foundation for exploring one-dimensional van der Waals materials as tunable hosts for defect-induced spin defects, paving the way for advancements in quantum technologies.