{
  "abstract": "The simultaneous suppression of particle-like ($κ_p$ ) and wave-like ($κ_c$) thermal transport channels in crystalline materials remains a challenging problem, as reducing one channel can enhance the other. Here, we investigate the thermal transport in trigonal $P\\Bar{3}m1$ CsAg$_3$S$_2$ using self-consistent phonon theory with cubic and quartic anharmonicity and the unified theory of thermal transport. Our calculations predict an ultralow lattice thermal conductivity of 0.222 W m$^{-1}$ K$^{-1}$ at 300 K, featuring simultaneously low $κ_p$ and $κ_c$ with a weak temperature dependence of $\\sim$T$^{-0.42}$, which deviates significantly from the conventional $\\sim$T$^{-1}$ behavior. This simultaneous suppression arises from localized Cs modes, which enhance anharmonic scattering, and the softer Ag-S framework, which reduces phonon group velocities, together suppressing $κ_p$, in conjunction with sparse, well-separated high-frequency S-derived optical modes that suppress $κ_c$ by limiting the coherent coupling between the phonon modes. Furthermore, the dominant transport channel exhibits a temperature-dependent crossover, with $κ_p$ contributing $\\sim$74 \\% of total lattice thermal conductivity at 300~K and $κ_c$ contributing $\\sim$63 \\% at 700~K. Combining the ultralow thermal conductivity with electrical transport calculated within the momentum relaxation time approximation (MRTA), we obtain a $ZT$ of 1.28 for $n$-type doping at 700 K. The present work not only clarifies the microscopic mechanism of ultralow thermal conductivity in trigonal CsAg$_3$S$_2$ but also identifies the covalent M-Ch framework modification within the AM$_3$Ch$_2$ family of ternary chalcogenides as an additional tuning parameter for further reducing $κ_p$ within the bonding-hierarchy design principle.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.35360",
  "author_total": 2,
  "authors": [
    {
      "name": "Vivek Gusain"
    },
    {
      "name": "B K Mani"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/2aj41xzbes9ww.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.35360",
  "fulltext_url": null,
  "id": "2aj41xzbes9ww",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.35360",
  "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.mtrl-sci"
    ],
    [
      "openalex",
      "2505|Thermal properties of materials"
    ]
  ],
  "openalex": "W7224004346",
  "pdf_url": "https://arxiv.org/pdf/2610.35360",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-22",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/2aj41xzbes9ww.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:35:35Z",
      "native_id": "2610.35360",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.35360"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.mtrl-sci",
      "subfield": "condensed-matter"
    }
  ],
  "title": "Simultaneous suppression and temperature-driven crossover of particle-like and wave-like thermal transport in trigonal CsAg$_3$S$_2$",
  "title_text": "Simultaneous suppression and temperature-driven crossover of particle-like and wave-like thermal transport in trigonal CsAg_3S_2",
  "type": "preprint",
  "updated_at": "2026-10-30T12:35:35Z",
  "url": "https://research.draconitic.com/paper/2aj41xzbes9ww",
  "venue": "arXiv",
  "versions": []
}