Crystalline Order Yet Glass-Like Heat Transport Driven by Hidden Local Distortions as the Structural Origin of Ultralow Thermal Conductivity in AgErTe 2

作者：Debattam Sarkar, Shima Shahabfar, Yukun Liu, Premakumar Yanda, Thomas S. Ie, Hengdi Zhao, Pronoy Nandi, K. R. Pradeep, Chandra Shekhar, Claudia Felser, Vinayak P. Dravid, Chris Wolverton, Mercouri G. Kanatzidis · 发表于：Journal of the American Chemical Society · 年份：2025 · DOI：10.1021/jacs.5c16757 · 被引用次数：2 · 研究领域：Thermal properties of materials、Advanced Thermoelectric Materials and Devices、Thermography and Photoacoustic Techniques

Given their rich chemical diversity and the interplay among the p -, d -, and f -orbitals of chalcogens, transition metals, and lanthanides, respectively, rare-earth transition-metal chalcogenides exhibit a wide variety of structural, magnetic, and transport phenomena. As a result, they form a particularly appealing platform for investigating structure–property relationships, emergent electronic and magnetic behaviors, and thermal transport. Here we investigate AgErTe 2 as a model system to understand phonon-glass behavior in ordered crystalline solids, which establishes the design principles for thermal barrier coatings and next-generation thermoelectrics. The local bonding asymmetry and lattice softness suppress the inherently low lattice thermal conductivity, resembling the characteristics of amorphous materials. This suppression is significantly influenced by local off-centering of Ag atoms, which breaks lattice periodicity while maintaining global crystallinity. The presence of antibonding states just below the Fermi level, arising from Ag 4 d and Te 5 p orbital interactions, leads to lattice softening and destabilizes ideal tetrahedral coordination, resulting in a pseudo Jahn–Teller distortion. Furthermore, the coexistence of weaker, more polarizable Ag–Te bonds and stronger Er–Te bonds creates a complex vibrational landscape enriched with low-frequency modes and enhanced phonon scattering. A pronounced disparity in interatomic force constants gives rise to highly local...