Multiconfigurational study of negatively charged silicon vacancy in 4H-SiC*

Deep point defects in wide-gap semiconductors have emerged as promising systems for quantum information science applications. The prototype of such deep defects is the negatively charged nitrogen-vacancy defect in diamond. Recently, silicon carbide (SiC) has drawn attention as an alternative host for point defects due to its low price, mature fabrication technology, and telecom-range emission frequencies. A negatively charged silicon vacancy defect in 4H-SiC has a unique ground-state spin quartet and first-excited spin doublet with optical spin control and long spin coherence time. Although defect states inherently have many-electron characteristics, theoretical studies of defects are, so far, predominantly based on density-functional theory. We investigate the electronic structure of the Si vacancy defect by employing multiconfigurational quantum chemistry methods, including spin-orbit coupling. We recently demonstrated the predictive power of these methods by employing them to nitrogen vacancy center in diamond (Bhandari et al., Physical Review B 103, 014115 (2021)). For each defect, we determine the excitation energies between quartets and doublets, or within quartets or doublets, as well as the corresponding wave functions. Our results are compared to experimental data.