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arXiv · 2508.21670

Ultrafast heat transfer in single palladium nanocrystals seen with an X-ray free-electron laser

David Yang·James Wrigley·Jack Griffiths·Longlong Wu·Ana F. Suzana·Jiecheng Diao·Angel Rodriguez-Fernandez·Joerg Hallmann·Alexey Zozulya·Ulrike Boesenberg·Roman Shayduk·Jan-Etienne Pudell·Anders Madsen·Ian K. Robinson
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Abstract

We report transient highly strained structural states in individual palladium (Pd) nanocrystals, electronically heated using an optical laser, which precede their uniform thermal expansion. Using an X-ray free-electron laser probe, the evolution of individual 111 Bragg peaks is measured as a function of delay time at various laser fluences. Above a laser fluence threshold at a sufficient pump-probe delay, the Bragg peak splits into multiple peaks, indicating heterogeneous strain, before returning to a single peak, corresponding to even heat distribution throughout the lattice expanded crystal. Our findings are supported by a lattice displacement and strain model of a single nanocrystal at different delay times, which agrees with the experimental data. Our observations have implications for understanding femtosecond laser interactions with metals and the potential photo-catalytic performance of Pd.

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David Yang, James Wrigley, Jack Griffiths, Longlong Wu, Ana F. Suzana, Jiecheng Diao, Angel Rodriguez-Fernandez, Joerg Hallmann, Alexey Zozulya, Ulrike Boesenberg, Roman Shayduk, Jan-Etienne Pudell, Anders Madsen, Ian K. Robinson. 2026-02-09. Ultrafast heat transfer in single palladium nanocrystals seen with an X-ray free-electron laser. https://doi.org/10.1038/s43246-025-01063-z

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