Orbitally driven giant phonon anharmonicity in SnSe
Orbitally driven giant phonon anharmonicity in SnSe
复制标题
DOI：
10.1038/nphys3492
复制
发表时间：
2015-12-01
期刊：
影响因子：
19.6
通讯作者：
Delaire, O.
中科院分区：
文献类型：
--
作者：
Li, C. W.;Hong, J.;Delaire, O.
理解凝聚态系统中的元激发及其耦合对于开发更好的能量转换设备至关重要。在热电材料中，通过抑制负责宏观热输运的声子准粒子的传播来直接提高热电转换效率。目前热电转换效率的记录材料SnSe具有超低的热导率，但强烈的声子散射背后的机制在很大程度上仍然未知。从非弹性中子散射测量和第一性原理模拟，我们映射了四维声子色散表面的SnSe，并找到了起源的离子势非谐性负责的独特性质的SnSe。我们表明，巨声子散射来自于一个不稳定的电子结构，轨道相互作用导致的铁电晶格不稳定性。目前的结果提供了一个微观图片连接电子结构和声子非谐性SnSe，并提供了新的见解如何电子-声子和声子-声子相互作用可能导致实现超低热导率。
Understanding elementary excitations and their couplings in condensed matter systems is critical for developing better energy-conversion devices. In thermoelectric materials, the heat-to-electricity conversion efficiency is directly improved by suppressing the propagation of phonon quasiparticles responsible for macroscopic thermal transport. The current record material for thermoelectric conversion efficiency, SnSe, has an ultralow thermal conductivity, but the mechanism behind the strong phonon scattering remains largely unknown. From inelastic neutron scattering measurements and first-principles simulations, we mapped the four-dimensional phonon dispersion surfaces of SnSe, and found the origin of the ionic-potential anharmonicity responsible for the unique properties of SnSe. We show that the giant phonon scattering arises from an unstable electronic structure, with orbital interactions leading to a ferroelectric-like lattice instability. The present results provide a microscopic picture connecting electronic structure and phonon anharmonicity in SnSe, and offers new insights on how electron-phonon and phonon-phonon interactions may lead to the realization of ultralow thermal conductivity.