シャッタースピード1兆分の1秒の新型 “カメラ”で、原子の動的な乱れを見抜く(New “Camera” with Shutter Speed of 1 Trillionth of a Second Sees through Dynamic Disorder of Atoms)

カメラのシャッターを100万回高速化することで、材料が熱を移動させる仕組みを解明し、持続可能なエネルギー応用を進めるための大きな一歩となることがわかった Speeding up a camera shutter a million million times enables researchers to understand how materials move heat around and is a major step in advancing sustainable energy applications

2023-03-07 コロンビア大学

＜関連情報＞

• https://www.engineering.columbia.edu/news/new-camera-shutter-speed-sees-through-dynamic-disorder-atoms
• https://www.nature.com/articles/s41563-023-01483-7

動的結晶構造解析による立方晶GeTeの自発的異方性の解明 Dynamic crystallography reveals spontaneous anisotropy in cubic GeTe

Simon A. J. Kimber,Jiayong Zhang,Charles H. Liang,Gian G. Guzmán-Verri,Peter B. Littlewood,Yongqiang Cheng,Douglas L. Abernathy,Jessica M. Hudspeth,Zhong-Zhen Luo,Mercouri G. Kanatzidis,Tapan Chatterji,Anibal J. Ramirez-Cuesta & Simon J. L. Billinge
Nature Materials  Published20 February 2023
DOI:https://doi.org/10.1038/s41563-023-01483-7

Abstract

Cubic energy materials such as thermoelectrics or hybrid perovskite materials are often understood to be highly disordered^1,2. In GeTe and related IV–VI compounds, this is thought to provide the low thermal conductivities needed for thermoelectric applications¹. Since conventional crystallography cannot distinguish between static disorder and atomic motions, we develop the energy-resolved variable-shutter pair distribution function technique. This collects structural snapshots with varying exposure times, on timescales relevant for atomic motions. In disagreement with previous interpretations^3,4,5, we find the time-averaged structure of GeTe to be crystalline at all temperatures, but with anisotropic anharmonic dynamics at higher temperatures that resemble static disorder at fast shutter speeds, with correlated ferroelectric fluctuations along the <100>_c direction. We show that this anisotropy naturally emerges from a Ginzburg–Landau model that couples polarization fluctuations through long-range elastic interactions⁶. By accessing time-dependent atomic correlations in energy materials, we resolve the long-standing disagreement between local and average structure probes^1,7,8,9 and show that spontaneous anisotropy is ubiquitous in cubic IV–VI materials.