Dipolar spin relaxation of divacancy qubits in silicon carbide

Abstract

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 T1 drops resonantly due to the coupling to either nuclear spins or electron spins. We quantitatively analyze the dependence of the T1 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.

Low-field microwave-free sensors using dipolar spin relaxation of quartet spin states in silicon carbide

“…More information on relevant paramagnetic defects in SiC can be found in Ref. [15]. Nuclear and electron baths are considered independently and calculated separately.…”

“…[34] and summarized in Ref. [15]. This method uses an extended Lindbladian to facilitate effective interactions.…”

“…The presence of the bias field is often undesirable as it may perturb the sample and influence the measurement. [10][11][12][13] Relaxometry-based sensing has not been explored for other point defect qubits, such as the divacancy 14,15 and the negatively charged silicon vacancy [16][17][18] in silicon carbide (SiC). 15 The latter defect is, however, attractive for low magnetic field relaxometry applications owing to its small zero-field splitting value and resulting quasi degenerate electron spin states.…”

“…[10][11][12][13] Relaxometry-based sensing has not been explored for other point defect qubits, such as the divacancy 14,15 and the negatively charged silicon vacancy [16][17][18] in silicon carbide (SiC). 15 The latter defect is, however, attractive for low magnetic field relaxometry applications owing to its small zero-field splitting value and resulting quasi degenerate electron spin states. For such applications, a detailed understanding of the relaxation processes of this defect is crucial.…”

“…21,29,30 The external field dependence of the relaxation processes have received little attention thus far, but must be understood in detail for various relaxometry applications. Recent theoretical developments have enabled parameter-free calculations of the two major contributions to the longitudinal spin relaxation, namely the temperature dependent spin-lattice relaxation [31][32][33] and the magnetic field dependent dipolar spin relaxation induced by local environmental spins 15,34,35 .…”