{
  "abstract": "In local theories with short-range interactions, continuous symmetries cannot be spontaneously broken in two spatial dimensions at nonzero temperature. $\\mathrm{U}(1)$-symmetric models instead admit a Berezinskii--Kosterlitz--Thouless (BKT) phase with quasi-long-range order and nonzero phase stiffness, which is normally destroyed at high temperatures by vortex proliferation. Here, we show that a BKT phase, and with it superfluidity, can persist to arbitrarily high temperatures. Using the large-$N$ expansion, we study a $(2+1)$-dimensional quantum field theory in which a complex scalar is coupled to the critical $\\mathrm{O}(N)$ model. At the biconical fixed point, where the inter-sector coupling is negative, the thermal effective potential has a circle of minima with nonzero $\\mathrm{U}(1)$ amplitude. Integrating out the gapped fluctuations yields an effective theory for the compact phase mode at distances large compared to $1/T$. Since temperature is the only scale at the fixed point, the phase stiffness grows linearly with temperature, with a proportionality factor that scales linearly with $N$ and is fixed entirely by the fixed point. This renders vortex operators irrelevant for sufficiently large $N$. We further show that the vortex fugacity is exponentially small in $N$.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.20717",
  "author_total": 4,
  "authors": [
    {
      "name": "Bilal Hawashin"
    },
    {
      "name": "Soumyadeep Chaudhuri"
    },
    {
      "name": "Igor F. Herbut"
    },
    {
      "name": "Michael M. Scherer"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/6jt2627pem1f9.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.20717",
  "fulltext_url": null,
  "id": "6jt2627pem1f9",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.20717",
  "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",
      "cond-mat.stat-mech"
    ],
    [
      "arxiv",
      "cond-mat.str-el"
    ],
    [
      "arxiv",
      "hep-th"
    ],
    [
      "openalex",
      "3104|Theoretical and Computational Physics"
    ]
  ],
  "openalex": "W7222731670",
  "pdf_url": "https://arxiv.org/pdf/2610.20717",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-14",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/6jt2627pem1f9.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:29:50Z",
      "native_id": "2610.20717",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.20717"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.str-el",
      "subfield": "condensed-matter"
    },
    {
      "field": "physics",
      "origin": "arxiv:hep-th",
      "subfield": "high-energy"
    },
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.stat-mech",
      "subfield": "statistical-nonlinear"
    }
  ],
  "title": "All-temperature superfluidity in two dimensions",
  "title_text": "All-temperature superfluidity in two dimensions",
  "type": "preprint",
  "updated_at": "2026-10-30T12:29:50Z",
  "url": "https://research.draconitic.com/paper/6jt2627pem1f9",
  "venue": "arXiv",
  "versions": []
}