The effect of quantum vibronic coupling on the electronic properties of color centers

Color centers in wide band gap semiconductors are promising candidates for solid-state quantum technologies. Their defect levels are usually well localized in space as well as in energy, within the band gap of the material, thus minimizing the interactions between the defect and the host and leading to relatively long coherence times. However, the electron-phonon interaction between the defect states and the atomic vibrations of the system may yield an undesired coupling between defects and the host, thus affecting the coherence times. We present calculations of the electronic Green’s function of the defect states in the presence of the host lattice vibrations, using first-principle many-body perturbation theory. We focus on the prototypical NV^- center in diamond and show that even at 0 K, the single-particle energy levels fluctuate within an interval of about 0.5 eV, due to quantum vibronic coupling. We discuss the temperature dependence of the photoemission and inverse photoemission spectra of the NV- in diamond, as well as the extension of the formalism used here to compute other properties such as photoluminescence and magnetic resonance spectra.