{
  "abstract": "High-temperature superconductivity has been found in bilayer Ruddlesden-Popper (RP) nickelates in bulk samples under high pressure, or in thin films via compressive strain. In the superconducting state, a tetragonal structure with a straight Ni-O-Ni bond along c-axis has been commonly observed, together with the suppression or diminishing of the density-wave orders. Therefore, it remains an open question whether these factors are sufficient for achieving superconductivity at ambient pressure. Here we report the first successful synthesis of heavily Sr-doped La$_{2}$SrNi$_{2}$O$_{7-δ}$ under high-pressure and high-temperature (HPHT) conditions with a flux method. X-ray diffraction and scanning transmission electron microscopy (STEM) confirm that the material adopts a tetragonal (I4/mmm) structure with an 180$^{\\circ}$ Ni-O-Ni bond angle along c-axis. Resistance measurements reveal metallic behavior with a low-temperature upturn and no density-wave features are observed. However, neither pressure nor oxygen variation induces superconductivity. Density functional theory calculations indicate that the holes introduced by Sr doping are predominantly doped into the Ni-3d$_{z^2}$ orbital, leading to the appearance of a very large $γ$ pocket on the Fermi surface at ambient pressure and significantly reducing the occupation of the Ni-3d$_{z^2 }$ orbital. Combining the experimental observations with theoretical calculations, we attribute the absence of superconductivity to the serious deviation from the half-filling state of the Ni-3d$_{z^2 }$ band, which is crucial for the interlayer antiferromagnetic interaction and thus for pairing. Our work unravels important issues for achieving superconductivity in bilayer nickelate system.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.00542",
  "author_total": 11,
  "authors": [
    {
      "name": "Yuhang Zhang"
    },
    {
      "name": "Xue Ming"
    },
    {
      "name": "Cui-Qun Chen"
    },
    {
      "name": "Wei Chen"
    },
    {
      "name": "Tian-Yi Li"
    },
    {
      "name": "Zhe-Ning Xiang"
    },
    {
      "name": "Qing Li"
    },
    {
      "name": "Bing-hui Ge"
    },
    {
      "name": "Dao-Xin Yao"
    },
    {
      "name": "Xiyu Zhu"
    },
    {
      "name": "Hai-Hu Wen"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/0wgdfj6f3qme4.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.00542",
  "fulltext_url": null,
  "id": "0wgdfj6f3qme4",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.00542",
  "language": null,
  "licence": "CC-BY-NC-SA-4.0",
  "licence_label": "CC BY-NC-SA 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by-nc-sa/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "cond-mat.mtrl-sci"
    ],
    [
      "arxiv",
      "cond-mat.supr-con"
    ],
    [
      "openalex",
      "3104|Physics of Superconductivity and Magnetism"
    ]
  ],
  "openalex": "W7206165478",
  "pdf_url": "https://arxiv.org/pdf/2609.00542",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/0wgdfj6f3qme4.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:00Z",
      "native_id": "2609.00542",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.00542"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.mtrl-sci",
      "subfield": "condensed-matter"
    }
  ],
  "title": "Heavily Sr-Doped La$_{2}$SrNi$_{2}$O$_{7-δ}$ as a Tetragonal Ruddlesden-Popper Phase at Ambient Pressure",
  "title_text": "Heavily Sr-Doped La_2SrNi_2O_7−δ as a Tetragonal Ruddlesden-Popper Phase at Ambient Pressure",
  "type": "preprint",
  "updated_at": "2026-10-30T12:18:00Z",
  "url": "https://research.draconitic.com/paper/0wgdfj6f3qme4",
  "venue": "arXiv",
  "versions": []
}