Figure 4. Effective decoupling of the ¹³C and ²⁹Si spin baths in 4H–SiC.

(a) The theoretical Hahn-echo coherence function of the divacancy ensemble at B=30 mT, calculated by only including the single- and heterogeneous pair-correlation contributions as defined in equation (3) and by varying the gyromagnetic ratio of ²⁹Si (γ_Si) as a theoretical parameter while that of ¹³C (γ_C) is fixed at its experimental value. (b) The average number of homogeneous nuclear spin pairs whose lengths are <6 Å, as a function of distance from the divacancy qubit in 4H–SiC and from the NV centre in diamond. The centre-of-mass of a nuclear spin pair is used to measure the distance from the qubit. (c) The spatial distribution of homogeneous nuclear spin pairs in 4H–SiC and in diamond. The shortest homogeneous nuclear spin pair in diamond is 1.54 Å, corresponding to the C–C bond length, while that of the homogeneous nuclear spin pair in 4H–SiC is 3.07 Å, which is the second nearest neighbouring Si–Si or C–C distances.