2023-10-06 デンマーク工科大学(DTU)
◆この技術は、光子結晶や新しい太陽電池の開発など、様々な結晶材料に適用可能であり、科学研究に革新をもたらす可能性があります。
＜関連情報＞
- https://www.fysik.dtu.dk/english/about/news/forskere-filmer-lydboelger-i-en-krystal
- https://www.pnas.org/doi/10.1073/pnas.2307049120
X線顕微鏡で固体材料中の音波をリアルタイムイメージング Real-time imaging of acoustic waves in bulk materials with X-ray microscopy
Theodor S. Holstad, Leora E. Dresselhaus-Marais, Trygve Magnus Ræder, Bernard Kozioziemski, Tim van Driel, Matthew Seaberg, Eric Folsom, Jon H. Eggert, Erik Bergbäck Knudsen, Martin Meedom Nielsen, Hugh Simons, Kristoffer Haldrup, and Henning Friis Poulsen
Proceedings of the National Academy of Sciences Published:September 19, 2023
DOI:https://doi.org/10.1073/pnas.2307049120
Significance
In this work, we present ultrafast (subpicosecond), submicrometer-resolution direct imaging of phonon propagation in bulk materials. To achieve this, we developed a unique X-ray diffraction microscopy technique for capturing minute lattice perturbations in deeply embedded volumes. This result is significant because phenomena occurring at timescales dictated by lattice dynamics are ubiquitous (e.g., displacive phase transformations, acoustic wave propagation, and ballistic thermal transport), yet the means for nondestructively imaging the structural changes associated with these phenomena have—until now—been six orders of magnitude too slow. The approach is generally applicable to all types of crystalline matter and will therefore be broadly relevant across solid-state physics, as well as materials science and geoscience.
Abstract
The dynamics of lattice vibrations govern many material processes, such as acoustic wave propagation, displacive phase transitions, and ballistic thermal transport. The maximum velocity of these processes and their effects is determined by the speed of sound, which therefore defines the temporal resolution (picoseconds) needed to resolve these phenomena on their characteristic length scales (nanometers). Here, we present an X-ray microscope capable of imaging acoustic waves with subpicosecond resolution within mm-sized crystals. We directly visualize the generation, propagation, branching, and energy dissipation of longitudinal and transverse acoustic waves in diamond, demonstrating how mechanical energy thermalizes from picosecond to microsecond timescales. Bulk characterization techniques capable of resolving this level of structural detail have previously been available on millisecond time scales—orders of magnitude too slow to capture these fundamental phenomena in solid-state physics and geoscience. As such, the reported results provide broad insights into the interaction of acoustic waves with the structure of materials, and the availability of ultrafast time-resolved dark-field X-ray microscopy opens a vista of new opportunities for 3D imaging of materials dynamics on their intrinsic submicrosecond time scales.
