Speaker
Description
Prototypical Color Centers in semiconductors, such as the $\mathrm{NV^-}$-center in diamond, the Silicon vacancy ($\mathrm{V_{Si}^-}$) and the di-vacancy ($\mathrm{V_{C}V_{Si}}$) in 4H-Silicon carbide (4H-SiC) are promising candidates for the implementation of quantum bits (qubits) in semiconductors. Their coupled electron spins exhibit correlated high- and low-spin states,enabling spin-selective manipulation via optical excitation, magnetic fields or strain. Optical spin manipulation involves excitations within the high-spin multiplet and spin-selective non-radiative transitions (intersystem-crossing, ISC), mediated by spin-orbit,spin-spin, and electron-phonon interactions. Together with the zero-field splitting in ground and excited states, these processes enable diverse spin-photon protocols. A quantitative understanding of spin-selective interactions is essential for optimizing such quantum interfaces. We describe Color Centers using an embedding approach based on a configuration-interaction (CI) Hamiltonian with an effective screened Coulomb interaction [1,2], extended by a perturbative treatment of the spin-orbit coupling [3]. In combination with the electron-phonon coupling this framework provides access to spin-selective transition rates and photo ionization [3,4]. We demonstrate the approach by analyzing the spin-selective optical cycle of the $\mathrm{V_{Si}^-}$ in 4H-SiC. Our results yield a quantitative understanding of the underlying processes and open the door to theory-guided qubit engineering.
[1] M. Bockstedte et al., npj Quantum Materials 3, 31 (2018).
[2] M. Niethammer et al., Nano Letter 19, 7173 (2019).
[3] M. Neubauer et al., Key Eng. Mat. 984, 1 (2023).
[4] T. Steidl et al., Nat. Commun. 16, 4669 (2025).
