Spin Structure and Resonant Driving of Spin-1/2 Defects in SiC

Transition metal (TM) defects in silicon carbide have favorable spin coherence properties and are suitable as quantum memory for quantum communication. To characterize TM defects as quantum spin-photon interfaces, we model defects that have one active electron with spin 1/2 in the atomic $D$ shell. The spin structure, as well as the magnetic and optical resonance properties of the active electron emerge from the interplay of the crystal potential and spin-orbit coupling and are described by a general model derived using group theory. We find that the spin-orbit coupling leads to additional allowed transitions and a modification of the $g$-tensor. To describe the dependence of the Rabi frequency on the magnitude and direction of the static and driving fields, we derive an effective Hamiltonian. This theoretical description can also be instrumental to perform and optimize spin control in TM defects.