Relaxation dynamics of spin-3/2 silicon vacancies in 4H-SiC

Room-temperature optically detected magnetic resonance experiments on spin- 3 2 silicon vacancies in 4H-SiC are reported. The ms = +1 2 ↔ −1 2 transition is accessed using a two-microwave-frequency excitation protocol. The ratio of the Rabi frequencies of the +3 2 ↔ +1 2 and +1 2 ↔ −1 2 transitions is measured to be (0.901 ± 0.013). The deviation from √3/2 is attributed to small difference in g factor for different magnetic dipole transitions. Whereas a spin- 1 2 system is characterized by a single-spin lifetime T1, we experimentally demonstrate that the spin- 3 2 system has three distinct relaxation modes that can be preferentially excited and detected. The measured relaxation times are (0.41 ± 0.02)Tslow = Td = (3.3 ± 0.5)Tfast. This differs from the values of Tp/3 = Td = 2Tf expected for pure dipole (Tp), quadrupole (Td ), and octupole (Tf ) relaxation modes, respectively, and implies admixing of the slow dipole and fast octupole relaxation modes.