Initial Atomic Motion Immediately Following Femtosecond-Laser Excitation in Phase-Change Materials

E. Matsubara, S. Okada, T. Ichitsubo, T. Kawaguchi, Akihiko Hirata, P. F. Guan, K. Tokuda, K. Tanimura, T. Matsunaga, M. W. Chen, N. Yamada

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Abstract

Despite the fact that phase-change materials are widely used for data storage, no consensus exists on the unique mechanism of their ultrafast phase change and its accompanied large and rapid optical change. By using the pump-probe observation method combining a femtosecond optical laser and an x-ray free-electron laser, we substantiate experimentally that, in both GeTe and Ge2Sb2Te5 crystals, rattling motion of mainly Ge atoms takes place with keeping the off-center position just after femtosecond-optical-laser irradiation, which eventually leads to a higher symmetry or disordered state. This very initial rattling motion in the undistorted lattice can be related to instantaneous optical change due to the loss of resonant bonding that characterizes GeTe-based phase change materials. Based on the amorphous structure derived by first-principles molecular dynamics simulation, we infer a plausible ultrafast amorphization mechanism via nonmelting.

Original languageEnglish
Article number135501
JournalPhysical Review Letters
Volume117
Issue number13
DOIs
Publication statusPublished - 2016 Sep 21
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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    Matsubara, E., Okada, S., Ichitsubo, T., Kawaguchi, T., Hirata, A., Guan, P. F., Tokuda, K., Tanimura, K., Matsunaga, T., Chen, M. W., & Yamada, N. (2016). Initial Atomic Motion Immediately Following Femtosecond-Laser Excitation in Phase-Change Materials. Physical Review Letters, 117(13), [135501]. https://doi.org/10.1103/PhysRevLett.117.135501