Benjamin Whitefield
University of Technology Sydney, Ultimo, Australia _______________________________________
Electron spins coupled with optical transitions in solids stand out as a promising platform for developing spin-based quantum technologies. Recently, hexagonal boron nitride (hBN) – a layered Van der Waals (vdW) crystal, has emerged as a promising host for optically addressable spin systems. Despite the significant progress in identifying single spin defects in hBN, exploration and utilization of these spin defects in quantum technologies remain largely untouched primarily due to challenges in deterministic fabrication of the defects and suboptimal spectral properties. In as-grown hBN films and treated hBN powders or flakes, the probability of identifying a single emitter with spin transitions is 5%, with only 1 in 20 emitters exhibiting optically active spin transitions[1,2]. Moreover, the spectral emissions recorded from these emitters in previous reports are broad, making them less appealing for quantum applications.In this study, we controllably engineer spin defects in multilayer pristine hBN flakes and carbon-doped hBN (c-hBN) using an oxygen-annealing process. Our results demonstrate a robust protocol where over 25% of the emitters exhibit a clear signature of an optical spin readout at room temperature, surpassing all previously reported results by an order of magnitude. Previous studies on similar spin defects have observed S = 1 or S = 1/2 transitions separetely[1-4], however the spin defects generated in this study exhibit both simultaneously. The origins of the spin dependent emission of these spin complexes is explained by charge transfer from strongly to weakly coupled spin pairs[4]. Through density functional theory, a potential defect structure is proposed for the two defects involved in the charge transfer.Our work provides a solid groundwork for activation of narrowband single photon emitters in hBN across the visible range. The study also advances the understanding of spin complexes in hBN and sets the stage for single spin – photon interfaces in layered vdW materials with applications in quantum sensing and information processing.
References
[1] Stern, H. L. et al. Room-temperature optically detected magnetic resonance of single defects in hexagonal boron nitride. Nature Communications 13, 618 (2022). https://doi.org/10.1038/s41467-022-28169-z
[2] Patel, R. N. et al. Room Temperature Dynamics of an Optically Addressable Single Spin in Hexagonal Boron Nitride. Nano Letters 24, 7623-7628 (2024). https://doi.org/10.1021/acs.nanolett.4c01333
[3] Stern, H. L. et al. A quantum coherent spin in hexagonal boron nitride at ambient conditions. Nature Materials 23, 1379-1385 (2024). https://doi.org/10.1038/s41563-024-01887-z
[4] Robertson, I. O. et al. A universal mechanism for optically addressable solid-state spin pairs. arXiv:2407.13148 (2024). https://ui.adsabs.harvard.edu/abs/2024arXiv240713148R
Email: benjamin.whitefield@student.uts.edu.au