{
  "abstract": "The coupling of excitons to lattice vibrations is typically treated via phenomenological models that artificially separate long-range Fröhlich and short-range Holstein interactions. Recent analytical work has established that, in the delocalized limit, Fröhlich scattering is suppressed by electron--hole interference. Here we present a model-space Bethe--Salpeter framework to evaluate exciton--phonon coupling across the extended-to-localized crossover. We establish a fundamental distinction between the \\emph{inclusive} exciton--phonon coupling weight, obtainable via an exact completeness sum rule without summation over excited states, and the \\emph{exclusive} intraband (internal-state-preserving) scattering amplitude that governs low-energy decoherence. We prove an exact symmetry theorem: for an inversion-symmetric relative-coordinate Hamiltonian with equal electron and hole masses, the intraband Fröhlich vertex vanishes identically, protecting the exciton from low-energy polar phonon scattering. When mass asymmetry is introduced, the finite-momentum relative wavefunction acquires a complex phase twist that breaks this protection. By analyzing the long-wavelength limit, we derive a controlled small-$q$ activation law showing that the intraband vertex scales as $F_{00}(q) \\propto Δq^2 \\langle r^2 \\rangle$, where $Δ$ parameterizes the mass asymmetry. Finally, we compute the second-order polaron self-energy shift and demonstrate that mass asymmetry dramatically enhances phonon dressing, confirming that the symmetry theorem directly governs the many-body energy renormalization of the exciton. These results provide a rigorous conceptual framework for understanding the competition between long-range and local exciton--phonon coupling in polar semiconductors.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.29634",
  "author_total": 1,
  "authors": [
    {
      "name": "Michael O. Atambo"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/256mn267ptbr8.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.29634",
  "fulltext_url": null,
  "id": "256mn267ptbr8",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.29634",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "cond-mat.mtrl-sci"
    ],
    [
      "openalex",
      "3107|Semiconductor Quantum Structures and Devices"
    ]
  ],
  "openalex": "W7214365386",
  "pdf_url": "https://arxiv.org/pdf/2609.29634",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/256mn267ptbr8.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:24:11Z",
      "native_id": "2609.29634",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.29634"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.mtrl-sci",
      "subfield": "condensed-matter"
    }
  ],
  "title": "Symmetry-protected intraband exciton-phonon scattering and its breakdown by mass asymmetry",
  "title_text": "Symmetry-protected intraband exciton-phonon scattering and its breakdown by mass asymmetry",
  "type": "preprint",
  "updated_at": "2026-10-30T12:24:11Z",
  "url": "https://research.draconitic.com/paper/256mn267ptbr8",
  "venue": "arXiv",
  "versions": []
}