Dipolar spin relaxation of divacancy qubits in silicon carbide

Abstract

Divacancy spins in silicon carbide implement qubits with outstanding characteristics and capabilities, including but not limited to, 64 ms coherence time, spin-to-photon interfacing, and sizable, 10% − 30% room-temperature read-out contrast, all of these in an industrial semiconductor host. Despite these great demonstrations, there are still numerous open questions on the physics of divacancy point defects. In particular, spin relaxation, which sets the fundamental limit for the spin coherence time, has not been thoroughly studied yet. Here, we carry out theoretical simulations of environmental spin induced spin relaxation processes of different divacancy configurations in 4H-SiC. We reveal magnetic field values where the longitudinal spin relaxation time T 1 drops resonantly due to the coupling to either 29 Si and 13 C nuclear spins or electron spins associated with other defects and dopants. We quantitatively analyze the dependence of the T 1 time on the concentration of the defect spins and the applied magnetic field in the most relevant cases and provide a simple analytical expression allowing either for estimation of the T 1 time in samples with known spin defect concentration or for estimation of the local spin defect concentration of an ensemble or a single divacancy qubit from the measured relaxation rates.

Spin Polarization, Electron–Phonon Coupling, and Zero-Phonon Line of the NV Center in 3C-SiC

“…As the measurements were done at a magnetic field of 2870 G, the ground state level anticrossing (GLAC) effects occuring in the magnetic field range B < 1000 G are not operative. For the actively studied axial divacancy centers in 4H-SiC, Lindvall et al [34] recently predicted the T 1 values of the order of 0.5 s, which is about an order of magnitude smaller than the value obtained for the NV center in 3C-SiC.…”

“…Its value is comparable to the case of the NV centers in diamond [31][32][33]. The spin lattice relaxation time is an important property of NV centers as it will limit or allow applications such as dynamic decoupling or sensing [34]. In general, it is associated with the electron-phonon interaction and describes the energy dissipation to the crystal lattice [35].…”