{
  "abstract": "Silicon color centers emitting in the near infrared offer a route to spin--photon interfaces compatible with mature complementary metal--oxide--semiconductor fabrication. A key unresolved candidate is the X-line at 1039.7 meV in the photoluminescence (PL) spectrum, long attributed to a complex of four self-interstitials (I$_4$), yet whose microscopic structure and spin properties have remained controversial and uncharacterized at a predictive level. Using hybrid-functional (HSE06) density functional theory, we unambiguously establish the bare I$_4$ complex as the origin of the X-line: our calculations quantitatively reproduce the zero-phonon line, the complete phonon sideband structure---identifying the prominent secondary peaks as one- and two-phonon replicas of strongly coupled quasi-local modes---and the EPR hyperfine constants. The charge transition level is found at VBM$+$0.08~eV, conclusively ruling out the previously proposed association with the B3 EPR center and its correlated deep donor level. Most significantly, we identify a metastable spin-1 triplet excited state separated from the singlet by $\\sim$1.6~meV, consistent with the NL51 EPR signal. The $D_{2d}$ symmetry of the defect suppresses intersystem crossing and phosphorescence by first-order spin--orbit coupling, implying an exceptionally long spin--lattice relaxation time. Combined with a spectrally resolvable zero-field splitting and near-infrared emission, the triplet state of the I$_4$ complex constitutes a viable spin quantum memory intrinsic to silicon.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.39713",
  "author_total": 7,
  "authors": [
    {
      "name": "Miaomiao Han"
    },
    {
      "name": "Song Li"
    },
    {
      "name": "Gergő Thiering"
    },
    {
      "name": "Thomas Frauenheim"
    },
    {
      "name": "Peter Deák"
    },
    {
      "name": "Bing Huang"
    },
    {
      "name": "Adam Gali"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/78z3vmh2fqqps.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.39713",
  "fulltext_url": null,
  "id": "78z3vmh2fqqps",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.39713",
  "language": null,
  "licence": "CC-BY-NC-ND-4.0",
  "licence_label": "CC BY-NC-ND 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "cond-mat.mtrl-sci"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2610.39713",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-29",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/78z3vmh2fqqps.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:36:23Z",
      "native_id": "2610.39713",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.39713"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.mtrl-sci",
      "subfield": "condensed-matter"
    }
  ],
  "title": "I$_4$ complex acting as near-infrared emitter with a quantum memory in silicon",
  "title_text": "I_4 complex acting as near-infrared emitter with a quantum memory in silicon",
  "type": "preprint",
  "updated_at": "2026-11-01T12:20:45Z",
  "url": "https://research.draconitic.com/paper/78z3vmh2fqqps",
  "venue": "arXiv",
  "versions": []
}