Theory of spin-orbit-phonon processes governing the anisotropic spin relaxation of SiV and other G4V centers in diamond

Anisotropy in spin relaxation times T₁, T₂ has previously been observed [1] in the neutral silicon-vacancy center (SiV⁰) of diamond. Here, we report similar strongly anisotropic behavior on negatively charged silicon SiV⁻. In conjunction with experimental work we develop the key elements of orbital and spin flipping processes induced by thermal phonons. We find that group theory considerations and selection rules are crucial to understand the observed anisotropy and thus we were able to distinguish the strength of pure orbital-phonon relaxation [2,3] and various other weaker diagonal and off-axis spin-orbit-phonon terms.

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In summary, in the present talk I will show excellent agreement with our experiments and depict a general theory that can be extended to other G4V (group-IV-vacancy) defect qubits straightforwardly that may highlight the limitations and caveats of their current quantum technology applications.

[1] B. C. Rose, G. Thiering, ... N. P. de Leon, Phys. Rev. B 98, 235140 (2018)

[2] K. D. Jahnke et. al. New J. Phys. 17 043011 (2015)

[3] I. B. W. Harris and D. Englund, Phys. Rev. B 109, 085414 (2024)