AI 中文总结
该研究评估热输运理论，采用机器学习原子间势和WTE框架，发现双通道机制主导超低κ材料热输运，预测结果与实验吻合，为相关器件设计提供基础。
AI 中文摘要
强非简谐晶体固体中的异常热输运对理论理解构成了基础挑战，同时为热电和热障涂层应用提供了机遇。尽管Green-Kubo理论能重现高温下的实验热导率（κ），但它缺乏微观洞察力，且忽略了晶格振动的玻色-爱因斯坦统计。另一方面，基于声子气图像的传统玻尔兹曼输运方程（BTE）框架因强非简谐性导致的过阻尼声子而失效。本文中，通过机器学习原子间势明确考虑温度相关的晶格动力学，并采用维格纳输运方程（WTE）框架，研究了硫族金属化合物TlAgSe和全无机层状Ruddlesden-Popper钙钛矿Cs₂PbI₂C₂的热输运性质。关键在于，热传导不仅由BTE描述的高阶声子散射主导的布居输运通道控制，还由WTE框架中本征态间类波分支间相干性产生的相干性通道控制。结合四声子散射，WTE预测室温下TlAgSe的平均κ值为0.31 Wm⁻¹K⁻¹，Cs₂PbI₂C₂的平均κ值为0.38 Wm⁻¹K⁻¹，与实验结果高度吻合。声子散射率分析揭示了强相干性的贡献和普遍存在的过阻尼声子模式，证明了仅基于一阶非简谐微扰的声子准粒子图像的传统BTE框架失效。该计算方法为超低κ材料中的热输运提供了统一描述，为声子和热电器件的合理设计提供了基础。
英文摘要
Anomalous heat transport in strongly anharmonic crystalline solids poses both a fundamental challenge to the theoretical understanding and an opportunity for thermoelectric and thermal barrier coating applications. Although Green-Kubo theory reproduces experimental thermal conductivity ($κ$) at high temperatures, it lacks microscopic insight and neglects the Bose-Einstein statistics of lattice vibrations. On the other hand, the conventional Boltzmann transport equation (BTE) framework, based on a phonon-gas picture, fails due to strong anharmonicity-induced overdamped phonons. Herein, the thermal transport properties in TlAgSe, a metal chalcogenide, and Cs$_2$PbI$_2$C$_2$, an all-inorganic layered Ruddlesden-Popper perovskite, are investigated by explicitly accounting for temperature-dependent lattice dynamics through machine learning interatomic potentials and employing the Wigner transport equation (WTE) framework. Crucially, heat conduction is governed not only by higher-order phonon scattering-dominated populations' transport channel described within the BTE, but also by a coherences' channel in the WTE framework arising from wave-like interbranch coherence between eigenstates. Incorporating four-phonon scattering, WTE predicts average room-temperature $κ$ values of 0.31 Wm$^{-1}$K$^{-1}$ (TlAgSe) and 0.38 Wm$^{-1}$K$^{-1}$ (Cs$_2$PbI$_2$C$_2$), in excellent agreement with experiments. Phonon scattering-rate analysis reveals strong coherences' contributions and prevalent overdamped phonon modes, demonstrating the breakdown of the conventional BTE framework based on the phonon quasiparticle picture with only first-order anharmonic perturbation. This computational approach provides a unified description of heat transport in ultralow-$κ$ materials, offering a basis for the rational design of phononic and thermoelectric devices.
