Temperature-dependent phonon-induced relaxation of the nitrogen-vacancy spin triplet in diamond

M. C. Cambria, A. Norambuena, H. T. Dinani, G. Thiering, A. Gardill, I. Kemeny, Y. Li, V. Lordi, A. Gali, J. R. Maze, S. Kolkowitz

Phonon-induced relaxation within the nitrogen-vacancy (NV) center's electronic ground-state spin triplet limits its coherence times, and thereby impacts its performance in quantum applications. We report measurements of the relaxation rates on the NV center's transitions as a function of temperature from 9 to 474 K in high-purity samples. Informed by ab initio calculations, we demonstrate that NV spin-phonon relaxation can be completely explained by the effect of second-order interactions with two distinct groups of quasilocalized phonons. Using a novel analytical model based on this understanding, we determine that the quasilocalized phonon groups are centered at 68.2(17) and 167(12) meV.