{
  "abstract": "The lower critical field $B_{c1}$ of a narrow superconducting thin-film strip sets the thermodynamic scale for vortex-free operation in a perpendicular magnetic field. The standard Pearl--London estimate requires a phenomenological vortex-core cutoff, because the London theory does not resolve the core. We formulate a microscopic theory for a dirty strip by solving the two-dimensional Usadel equations in the film plane, with the applied field included directly in the gauge-invariant momentum. Self-consistent vortex and Meissner solutions are computed at fixed field, and $B_{c1}$ is obtained from their Gibbs-energy difference. The calculation resolves the vortex core and its finite-width deformation without introducing a cutoff. The resulting vortex self-energy is larger than the naive Pearl--London estimate and cannot, in general, be represented by a London logarithm with a single width-independent cutoff. The formulation applies at any $T<T_c$ and provides a microscopic basis for predicting $B_{c1}$ in superconducting nanostrips and related thin-film devices.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: Physical Review Applied 26, L031007 (2026)",
  "arxiv": "2607.05890",
  "author_total": 1,
  "authors": [
    {
      "name": "Takayuki Kubo"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/ddr7ez7wx1y1f.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2607.05890",
  "fulltext_url": null,
  "id": "ddr7ez7wx1y1f",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2607.05890",
  "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.supr-con"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2607.05890",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-22",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/ddr7ez7wx1y1f.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:34:34Z",
      "native_id": "2607.05890",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2607.05890"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.supr-con",
      "subfield": "condensed-matter"
    }
  ],
  "title": "Microscopic theory of the lower critical field in superconducting thin-film strips",
  "title_text": "Microscopic theory of the lower critical field in superconducting thin-film strips",
  "type": "preprint",
  "updated_at": "2026-10-30T12:34:34Z",
  "url": "https://research.draconitic.com/paper/ddr7ez7wx1y1f",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1103/l9v7-x1zb",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}