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

Creators: Huang, Yijing¹; Sun, Peihao²; Teitelbaum, Samuel W.²; Li, Haoyuan³; Sun, Yanwen; Wang, Nan; Song, Sanghoon; Sato, Takahiro; Chollet, Matthieu; Osaka, Taito⁴; Inoue, Ichiro⁴; Duncan, Ryan A.²; Shin, Hyun D.⁵; Haber, Johann²; Zhou, Jinjian⁶; Bernardi, Marco⁶; Gu, Mingqiang⁷; Rondinelli, James M.⁸; Trigo, Mariano²; Yabashi, Makina⁴; Maznev, Alexei A.⁵; Nelson, Keith A.⁵; Zhu, Diling; Reis, David A.²

1. University of Illinois Urbana-Champaign
2. SLAC National Accelerator Laboratory
3. Stanford University
4. SPring-8
5. Massachusetts Institute of Technology
6. California Institute of Technology
7. Southern University of Science and Technology
8. Northwestern University

Abstract

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 SrTiO₃ and KTaO₃ 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

Copyright and License (English)

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Acknowledgement (English)

The authors thank J. B. Hastings for useful discussions.

Funding (English)

This work was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES) through the Division of Materials Sciences and Engineering under Contract No. DE-AC02-76SF00515. Measurements were carried out at the Linac Coherent Light Source, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences under Contract No. DE AC02-76SF00515. Preliminary experiments were performed at SACLA with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (Proposal No. 2017B8046). P. S. acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant Agreement No. 101023787. The work of H. L. was supported by the U.S. DOE, Office of Science, BES under Award No. DE-SC0022222. The participants from M. I. T. were supported by the U.S. DOE, Office of Science, BES under Award No. DE-SC0019126. M. G. and J. M. R. were supported by the U.S. DOE under Grant No. DE-SC0012375.

Contributions (English)

Y. H., P. S., and S. W. T. contributed equally to this work.

Data Availability (English)

The data that support the findings of this study are openly available in Research Data Unipd at https://10.25430/researchdata.cab.unipd.it.00001361

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