{
  "abstract": "Quantum confinement restructures the electronic phase space of ultrathin metals, but the resulting density-of-states (DOS) change is not generically large. We show that, within a three-dimensional confinement theory based on the suppression of long-wavelength electronic states, the Fermi-level DOS enhancement on the weak-confinement branch is bounded by $(4/3)^{1/3}-1\\simeq10.1\\%$. Instead, confinement-induced redistribution of electronic phase space can be strongly amplified by resonant denominators in the second-order susceptibility. A minimal double-resonance closure predicts giant amplification when the film thickness approaches $L_c=(2π/n)^{1/3}$, where $n$ is the carrier density, and a dominant optical pathway lies within a dephasing linewidth of resonance. Applied to recent Ag(111) measurements, the theory gives an effective phase-space carrier density parameter $n_{\\rm eff}\\simeq3.6\\times10^{20}\\,\\mathrm{cm}^{-3}$, a tenfold enhancement of $|χ^{(2)}|$, and hence the observed $\\sim100$-fold increase of thickness-normalized second-harmonic-generation efficiency, together with the observed non-oscillatory thickness dependence.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.14468",
  "author_total": 1,
  "authors": [
    {
      "name": "Alessio Zaccone"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/8rgs7am8qnq1n.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.14468",
  "fulltext_url": null,
  "id": "8rgs7am8qnq1n",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.14468",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "cond-mat.mes-hall"
    ],
    [
      "arxiv",
      "cond-mat.other"
    ],
    [
      "arxiv",
      "physics.app-ph"
    ],
    [
      "arxiv",
      "physics.optics"
    ],
    [
      "arxiv",
      "quant-ph"
    ],
    [
      "openalex",
      "3107|Surface and Thin Film Phenomena"
    ]
  ],
  "openalex": "W7213300950",
  "pdf_url": "https://arxiv.org/pdf/2609.14468",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-13",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/8rgs7am8qnq1n.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:21:25Z",
      "native_id": "2609.14468",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.14468"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.app-ph",
      "subfield": "applied-instrumentation"
    },
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.mes-hall",
      "subfield": "condensed-matter"
    },
    {
      "field": "physics",
      "origin": "arxiv:physics.optics",
      "subfield": "optics-photonics"
    },
    {
      "field": "physics",
      "origin": "arxiv:quant-ph",
      "subfield": "quantum"
    }
  ],
  "title": "Giant second-harmonic generation in few-atomic layer metals",
  "title_text": "Giant second-harmonic generation in few-atomic layer metals",
  "type": "preprint",
  "updated_at": "2026-10-30T12:21:25Z",
  "url": "https://research.draconitic.com/paper/8rgs7am8qnq1n",
  "venue": "arXiv",
  "versions": []
}