{
  "abstract": "We present an \\textit{ab initio} description of the emergence and collapse of enhanced quadrupole collectivity in nuclei near $N=Z=40$ using multi-shell valence-space Hamiltonians derived from chiral two- and three-nucleon forces with the in-medium similarity renormalization group. Projected generator-coordinate calculations with consistently evolved $E2$ operators capture the strong collectivity in $^{80}$Zr and its decrease toward $^{86}$Mo and $^{88}$Ru without empirical effective charges. While the $N,Z=40$ effective single-particle energy gaps remain open, the $1g_{9/2}$--$2d_{5/2}$ spacing is smallest near $^{76}$Sr and $^{80}$Zr, with its variation governed mainly by the proton-neutron monopole contribution. The associated occupancies are consistent with quadrupole correlations involving pseudo-SU(3) $pf$ holes and quasi-SU(3) particles. Excluding the occupation of the proton and neutron $2d_{5/2}$ from the variational space strongly suppresses the deformation and $B(E2;2_1^+\\rightarrow0_1^+)$ in $^{80}$Zr. These results mark a steady step toward \\textit{ab initio} computations of heavy open-shell nuclei.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.15774",
  "author_total": 3,
  "authors": [
    {
      "name": "X. C. Cao"
    },
    {
      "name": "C. F. Jiao"
    },
    {
      "name": "R. Z. Hu"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/8jdkc4sampbst.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.15774",
  "fulltext_url": null,
  "id": "8jdkc4sampbst",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.15774",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "nucl-th"
    ],
    [
      "openalex",
      "3106|Nuclear physics research studies"
    ]
  ],
  "openalex": "W7213309820",
  "pdf_url": "https://arxiv.org/pdf/2609.15774",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-15",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/8jdkc4sampbst.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:21:41Z",
      "native_id": "2609.15774",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.15774"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:nucl-th",
      "subfield": "nuclear"
    }
  ],
  "title": "Ab Initio Emergence and Collapse of Nuclear Collectivity near N = Z = 40",
  "title_text": "Ab Initio Emergence and Collapse of Nuclear Collectivity near N = Z = 40",
  "type": "preprint",
  "updated_at": "2026-10-30T12:21:41Z",
  "url": "https://research.draconitic.com/paper/8jdkc4sampbst",
  "venue": "arXiv",
  "versions": []
}