TASQ Towards Scalable Quantum Technologies

• Younesi, Ali Tayefeh; Luu, Minh Tuan; Linderälv, Christopher; Zalandauskas, Vytautas; Bathen, Marianne Etzelmüller & Son, Nguyen Tien [Vis alle 10 forfattere av denne artikkelen] (2026). Unraveling the Electronic Structure of Silicon Vacancy Centers in 4H-SiC. Advanced Functional Materials. ISSN 1616-301X. 36(58). doi: 10.1002/adfm.76183. Fulltekst i vitenarkiv Vis sammendrag

  Point defects in silicon carbide (SiC), particularly the negatively-charged silicon vacancy (V−Si) in 4H-SiC, are leading candidates for scalable quantum technologies due to their favorable spin–optical properties and compatibility with industrial semiconductor fabrication processes. Comprehensive knowledge of a defect's electronic structure is essential for interpreting spin–optical dynamics and for the reliable design and optimization of defect-based quantum devices. Despite extensive study, our knowledge of the electronic structure of V−Si is limited since key excited-state manifolds have remained inaccessible to conventional steady-state spectroscopy. In this study, transient absorption spectroscopy is utilized to probe non-equilibrium electronic transitions of V−Si and to uncover previously unobserved excited states. The first direct observation of the elusive V2′ quartet transition is presented, with its broad spectral signature attributed to nonadiabatic vibronic coupling. Within the spin-doublet manifold, which is central to optically detected magnetic resonance (ODMR) but has remained unresolved spectroscopically, multiple optical transitions are identified. The complete electronic level structure in the relevant energy range is elucidated by combining polarization-resolved spectroscopy, group-theoretical analysis, quantum embedding calculations, and first-principles optical lineshape modeling. Collectively, these results provide a microscopic understanding of the V−Si electronic structure. Our approach also establishes a general framework for resolving and understanding complex excited-state manifolds in wide-bandgap color centers.

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