{
  "abstract": "Relativistic $5d$ Mott insulators host a rich variety of exotic hidden multipolar order, whose microscopic nature remains heavily debated. A broken local point-symmetry (BLPS) phase followed by antiferromagnetism was previously observed in the doped compound Ba$_2$Na$_{0.1}$Ca$_{0.9}$OsO$_6$, where mixed Os valence places the system toward the $5d^2$ end of the $5d^1$-$5d^2$ regime. In contrast, pristine $5d^2$ Ba$_2$CaOsO$_6$ has shown a single octupolar transition with average cubic symmetry, raising the question of whether BLPS arises from chemical disorder in the doped systems. Here, we discover the BLPS phase in pristine Ba$_2$CaOsO$_6$ emerging at $T^* \\approx 50$ K, precisely coincident with the octupolar transition. Beyond standard ${}^{43}$Ca nuclear magnetic resonance (NMR) spectral analysis, our spin-echo nutation measurements detect a finite electric field gradient, demonstrating spontaneous symmetry breaking despite the cubic average structure. While our NMR data support the previously identified octupolar order, the BLPS phase reveals a subdominant quadrupolar contribution, establishing that the hidden order in Ba$_2$CaOsO$_6$ is intrinsically multicomponent. Such mixed multipolar states lie beyond conventional theoretical descriptions of the $5d^2$ ground state. Our results establish local symmetry breaking as an intrinsic property of the clean $5d^2$ limit and provide a new constraint on microscopic theories of strongly spin-orbit-coupled Mott insulators.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.14223",
  "author_total": 8,
  "authors": [
    {
      "name": "Ilija K. Nikolov"
    },
    {
      "name": "Giuseppe Allodi"
    },
    {
      "name": "Ginevra Corsale"
    },
    {
      "name": "Anshu Kataria"
    },
    {
      "name": "Cierra Foster"
    },
    {
      "name": "Patrick Woodward"
    },
    {
      "name": "Samuele Sanna"
    },
    {
      "name": "Vesna F. Mitrović"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/c0yb74bhrzc3h.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.14223",
  "fulltext_url": null,
  "id": "c0yb74bhrzc3h",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.14223",
  "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.str-el"
    ],
    [
      "openalex",
      "3104|Advanced Condensed Matter Physics"
    ]
  ],
  "openalex": "W7213234815",
  "pdf_url": "https://arxiv.org/pdf/2609.14223",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-13",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/c0yb74bhrzc3h.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:21:25Z",
      "native_id": "2609.14223",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.14223"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.str-el",
      "subfield": "condensed-matter"
    }
  ],
  "title": "Emergence of Subdominant Quadrupolar Order in the 5$d^2$ Multipolar Mott Insulator Ba$_2$CaOsO$_6$",
  "title_text": "Emergence of Subdominant Quadrupolar Order in the 5d^2 Multipolar Mott Insulator Ba_2CaOsO_6",
  "type": "preprint",
  "updated_at": "2026-10-30T12:21:25Z",
  "url": "https://research.draconitic.com/paper/c0yb74bhrzc3h",
  "venue": "arXiv",
  "versions": []
}