Optically addressable spins in silicon carbide and related 2D materials: the effect of symmetry and spin-orbit coupling

Quantum technologies allow us to process and transfer information differently than classical information processing technologies. This thesis reports a study on isolated lattice defects with inherent quantum-mechanical behavior in silicon carbide, a semiconductor with well-established manufacturing techniques. Light that can travel through telecommunication fibers can be used to interlink defects that are spatially separated using existing infrastructure. Thus, we focus on defects that interact with telecom-compatible light, consisting of transition metal impurities in the SiC crystal. We use the spin of electrons in these systems as quantum information storage units.
Here, we present our insights on how the microscopic configuration of these defects influences their spin and their interaction with light. We find that when these defects are in particular lattice configurations their electrons have spins strongly pinned along a unique direction. When this happens, their quantum-state becomes very stable. Since there is a trade-off between the quantum-state stability and the possibility to control it, these geometries give rise to defects that are hard to control. We demonstrate that defects that contain a nuclear spin are easier to control than defects with no nuclear spin, but are also more easily disturbed by their environment. Finally, we show that the same physics responsible for the behavior of defects in SiC can be used to understand the behavior of spins in other materials with similar symmetries, like two-dimensional semiconductors.