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<p>Two-dimensional ferroelectric materials like NbOI<sub>2</sub> have garnered significant interest, yet their temporal response and synergetic interaction with light remain underexplored. Previous studies on the polarization of oxide ferroelectrics have relied on time-resolved optical second harmonic generation or ultrafast X-ray scattering. Here, we probe the laser-induced polarization dynamics of NbOI<sub>2</sub> nanocrystals using ultrafast transmission electron diffraction and deflectometry. The deflection of the electron pulses is directly sensitive to the changes in the polarization, while the diffraction signal captures the structural evolution. Excited with a UV laser pulse, the polarization of NbOI<sub>2</sub> is initially suppressed for two picoseconds, then it recovers and overshoots, leading to a transiently enhanced polarization persisting for over 200 ps. This recovery coincides with coherent acoustic phonon generation, triggering a piezoresponse in the NbOI<sub>2</sub> nanocrystals. Our results offer a new method for sensing the ferroelectric order parameter on femtosecond time scales.</p>

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Ultrafast dynamics of ferroelectric polarization of NbOI2 captured with femtosecond electron diffraction

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年8月30日

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  • Yibo Wang,
  • Md Sazzad Hossain,
  • Tianlin Li,
  • Yanwei Xiong,
  • Cuong Le,
  • Jesse Kuebler,
  • Nina Raghavan,
  • Lucia Fernandez-Ballester,
  • Xia Hong,
  • Alexander Sinitskii,
  • Martin Centurion

摘要

Two-dimensional ferroelectric materials like NbOI2 have garnered significant interest, yet their temporal response and synergetic interaction with light remain underexplored. Previous studies on the polarization of oxide ferroelectrics have relied on time-resolved optical second harmonic generation or ultrafast X-ray scattering. Here, we probe the laser-induced polarization dynamics of NbOI2 nanocrystals using ultrafast transmission electron diffraction and deflectometry. The deflection of the electron pulses is directly sensitive to the changes in the polarization, while the diffraction signal captures the structural evolution. Excited with a UV laser pulse, the polarization of NbOI2 is initially suppressed for two picoseconds, then it recovers and overshoots, leading to a transiently enhanced polarization persisting for over 200 ps. This recovery coincides with coherent acoustic phonon generation, triggering a piezoresponse in the NbOI2 nanocrystals. Our results offer a new method for sensing the ferroelectric order parameter on femtosecond time scales.