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arXiv · 2608.11687

First-principles cumulant approach to the vibronic structure of spin defects

Jinsoo Park·Yu Jin·Arpan Kundu·Jorge O. Sofo·Giulia Galli
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Abstract

Color centers in wide-band-gap semiconductors are leading platforms for solid-state quantum technologies, yet a quantitative description of their vibronic structure has remained elusive due to the complexity of multi-phonon processes in localized defect states. Here we present a first-principles Green's function framework based on the retarded cumulant ansatz (RCA) to describe electron-phonon interactions in spin defects; our approach goes beyond the adiabatic and lowest-order perturbation theory approximations underlying widely used approaches. Applied to the negatively charged nitrogen-vacancy (NV$^-$) center in diamond, our method reveals that multi-phonon satellites persist over a 400 meV energy window even at zero temperature, driven by quantum zero-point fluctuations. We demonstrate that accurate spectral functions require mode-, momentum-, spin-, and orbital-resolved electron-phonon matrix elements sampled across the full Brillouin zone, to account for hybridized and propagating phonon channels. We find that the vibronic structure of the NV$^-$ center exhibits strong spin and orbital anisotropy, with different orbitals coupling to qualitatively distinct parts of the phonon spectrum, and spin-selective coupling affecting both sideband positions and intensities.

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Jinsoo Park, Yu Jin, Arpan Kundu, Jorge O. Sofo, Giulia Galli. 2026-08-12. First-principles cumulant approach to the vibronic structure of spin defects. https://arxiv.org/abs/2608.11687

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