{
  "abstract": "Topological crystalline insulators extend the concept of topological insulators by hosting surface states protected by crystallographic symmetry. Their topological phase transitions arise from spin-orbit-driven band inversion in the bulk electronic structure, reshaping the low-energy electronic environment and its coupling to lattice excitations. While the electronic aspects of band topology are well established, the corresponding dynamics of lattice and electron-phonon interactions remain largely unexplored. Here, we report a pronounced softening of a low-energy surface phonon mode across the topological phase transition in Pb$_{0.77}$Sn$_{0.23}$Se, revealed by temperature-dependent time-domain terahertz spectroscopy. Unlike the well-known phonon softening in ferroelectrics, this effect does not signal a structural instability but instead reflects electronic reconstruction. We attribute the softening to the spectroscopic manifestations of a Kohn anomaly, indicating a strong coupling between lattice vibrations and Dirac-like surface electrons in the topological phase. Consistently, the phonon linewidth deviates from the standard anharmonic temperature dependence, further evidencing enhanced electron-phonon coupling. The observed changes in phonon frequency and linewidth at around 120 K are consistent with the reported topological phase transition temperature in this material. Our results thus provide a spectroscopic route for the distinct identification of the onset of a topological phase.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: Phys. Rev. B 114, 225111 (2026)",
  "arxiv": "2606.25381",
  "author_total": 7,
  "authors": [
    {
      "name": "Jingwen Li"
    },
    {
      "name": "Arpita Dutta"
    },
    {
      "name": "Kush Saha"
    },
    {
      "name": "Andrzej Szczerbakow"
    },
    {
      "name": "Tomasz Story"
    },
    {
      "name": "Manfred Fiebig"
    },
    {
      "name": "Shovon Pal"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/27j3dq336q2nz.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2606.25381",
  "fulltext_url": null,
  "id": "27j3dq336q2nz",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2606.25381",
  "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.str-el"
    ],
    [
      "openalex",
      "3107|Topological Materials and Phenomena"
    ]
  ],
  "openalex": "W7165971712",
  "pdf_url": "https://arxiv.org/pdf/2606.25381",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-16",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/27j3dq336q2nz.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:34:18Z",
      "native_id": "2606.25381",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2606.25381"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.str-el",
      "subfield": "condensed-matter"
    }
  ],
  "title": "Spectroscopic signatures of Kohn anomaly in a topological crystalline insulator",
  "title_text": "Spectroscopic signatures of Kohn anomaly in a topological crystalline insulator",
  "type": "preprint",
  "updated_at": "2026-10-30T12:34:18Z",
  "url": "https://research.draconitic.com/paper/27j3dq336q2nz",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1103/qg8k-y95s",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}