Dipolar spin relaxation of divacancy qubits in silicon carbide
Divacancy spins implement qubits with outstanding characteristics and capabilities in an industrial semiconductor host. On the other hand, there are still numerous open questions about the physics of these important defects, for instance, spin relaxation has not been thoroughly studied yet. Here, we carry out a theoretical study on environmental spin-induced spin relaxation processes of divacancy qubits in the 4H polytype of silicon carbide (4H-SiC). We reveal all the relevant magnetic field values where the longitudinal spin relaxation time T-1 drops resonantly due to the coupling to either nuclear spins or electron spins. We quantitatively analyze the dependence of the T-1 time on the concentration of point defect spins and the applied magnetic field and provide an analytical expression. We demonstrate that dipolar spin relaxation plays a significant role both in as-grown and ion-implanted samples and it often limits the coherence time of divacancy qubits in 4H-SiC. ; Funding Agencies|Knut and Alice Wallenberg Foundation through the WBSQD2 project [2018.0071]; Swedish Government Strategic Research Area SeRC; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; MTA Premium Postdoctoral Research Program; Hungarian NKFIH grants of the National Excellence Program of Quantum-coherent materials projectNational Research, Development & Innovation Office (NRDIO) - Hungary [KKP129866]; NKFIH through the National Quantum Technology ProgramNational Research, Development & Innovation Office (NRDIO) - Hungary [2017-1.2.1-NKP-2017-00001]; Quantum Information National Laboratory - Ministry of Innovation and Technology of Hungary; Swedish Research CouncilSwedish Research CouncilEuropean Commission [VR 2016-04068, 2018-05973]; EU H2020 project QuanTELCO [862721]