Nanometer-Scale Acoustic Wave Packets Generated by Stochastic Core-Level Photoionization Events

作者：Yijing Huang, Peihao Sun, Samuel W. Teitelbaum, Haoyuan Li, Yanwen Sun, Nan Wang, Sanghoon Song, Takahiro Sato, Matthieu Chollet, Taito Osaka, Ichiro Inoue, Ryan A. Duncan, Hyun D. Shin, Johann Haber, Jin-Jian Zhou, Marco Bernardi, Mingqiang Gu, James M. Rondinelli, Mariano Trigo, Makina Yabashi, A. A. Maznev, Keith A. Nelson, Diling Zhu, David A. Reis · 发表于：Physical Review X · 年份：2024 · DOI：10.1103/physrevx.14.041010 · 被引用次数：6 · 研究领域：Electronic and Structural Properties of Oxides、Nuclear Physics and Applications、High-pressure geophysics and materials

We demonstrate that the absorption of femtosecond hard x-ray pulses excites quasispherical, high-amplitude, and high-wave-vector coherent acoustic phonon wave packets using an all hard-x-ray pump-probe scattering experiment. The time- and momentum-resolved diffuse scattering signal is consistent with an ensemble of 3D strain wave packets induced by the rapid electron cascade dynamics following photoionization at uncorrelated excitation centers. We quantify key parameters of this process, including the localization size of the stress field and the photon energy conversion efficiency into elastic energy. The parameters are determined by the photoelectron and Auger electron cascade dynamics, as well as the electron-phonon interaction. In particular, we obtain the localization size of the observed strain wave packet to be 1.5 and 2.5 nm for bulk SrTiO 3 and KTaO 3 single crystals, respectively. The results provide crucial information on the mechanism of x-ray energy deposition into matter and shed light on the shortest collective length scales accessible to coherent acoustic phonon generation using x-ray excitation. Published by the American Physical Society 2024