标题： 晶体TlAgTe中类似玻璃的热导率的起源 显示英文标题

标题： Origin of Glass-like Thermal Conductivity in Crystalline TlAgTe

摘要： 有序晶体化合物表现出超低且类似玻璃的热导率，在基础和应用上都非常重要，其中声子准粒子主导了它们的热量传输。 理解支配这种异常传输行为的微观机制是必要的，以揭示这些准粒子的晶体结构、声子和集体激发之间的复杂相互作用。 在这里，我们使用基于量子密度泛函理论的最先进的第一性原理计算，研究半导体TlAgTe中实验测得的异常低且类似玻璃的热导率的起源。 利用一种结合声子自能引起的频率重正化、类粒子Peierls（$kappa_l^P$）和类波 coherent（$kappa_l^C$）热传输贡献以及三声子和四声子散射通道的非谐晶格动力学理论的统一框架，我们成功地从大小和温度依赖性方面解释了实验结果。 我们的分析表明，TlAgTe表现出几种局域化的声子模式，这些模式来源于Tl原子的协同振动，显示出强烈的温度依赖性和增强的四声子散射率，这些散射主要由Umklapp过程主导，将$kappa_l^P$抑制到极低值。 由此产生的由局部结构畸变、孤对电子和重阳离子的类似振动引起的强非谐性导致声子模式在40 cm$^-1$以上从类粒子行为过渡到类波隧穿特性，显著贡献于$kappa_l^C$，该值随温度增加而增加。 我们的分析揭示了重要的结构-性能关系，这可能用于设计具有可调热导率的新材料。 显示英文摘要

摘要： Ordered crystalline compounds exhibiting ultralow and glass-like thermal conductivity are both fundamentally and technologically important, where phonon quasi-particles dominate their heat transport. Understanding the microscopic mechanisms that govern such unusual transport behavior is necessary to unravel the complex interplay of crystal structure, phonons, and collective excitations of these quasi-particles. Here, we use state-of-the-art first-principles calculations based on quantum density functional theory to investigate the origin of experimentally measured unusually low and glassy thermal conductivity in semiconducting TlAgTe. Utilizing a unifying framework of anharmonic lattice dynamics theory that combine phonon self-energy induced frequency renormalization, particle-like Peierls ($kappa_l^P$) and wave-like coherent ($kappa_l^C$) thermal transport contributions including three and four-phonon scattering channels, we successfully explain the experimental results both in terms of magnitude and temperature dependence. Our analysis reveals that TlAgTe exhibits several localized phonon modes arising from concerted rattling-like vibration of Tl atoms, which show strong temperature dependence and enhanced four-phonon scattering rates that are dominated by Umklapp processes, suppressing $kappa_l^P$ to ultralow values. The ensuing strong anharmonicity induced by local structural distortions, lone-pair electrons, and rattling-like vibrations of the heavy cations lead to a transition from particle-like behavior to wave-like tunneling characteristics of the phonon modes above 40 cm$^-1$, contributing significantly to $kappa_l^C$ which increases with temperature. Our analysis uncovers important structure-property relationship, which may be used in designing of novel materials with tunable thermal conductivity.