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<p>Ultrafast coherent control of electric dipoles using terahertz pulses provides a means to discover hidden phases of materials and potentially leads to applications in high-speed optoelectronic devices. Although this approach has been shown to be effective in incipient ferroelectrics only close to the phase transition temperatures, it relies on the soft phonon modes overlapping with the terahertz pulse bandwidth. Because of their emergent subterahertz collective dynamics, a fundamentally distinct and effective terahertz coupling mechanism can be envisaged in topological polar structures in PbTiO<sub>3</sub>/SrTiO<sub>3</sub> superlattices. Here we demonstrate that polar skyrmions can be coherently driven into a hidden phase with transient macroscopic polarization, as probed using terahertz field-induced second-harmonic generation and optical Kerr effects. This ultrafast terahertz-driven phase transition is found to sustain across a broad temperature range of 4–470 K in a corresponding electric field required for equilibrium stability of skyrmions. Dynamical phase-field simulations reveal the correlation between the relaxation behaviour of the excited collective modes and the emergence of the polar phases. Our results manifest dynamical properties of topological polar structures, which could be technologically implemented given their flexibility in structure design and tunability under external electric fields.</p>

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Terahertz excitation of collective dynamics of polar skyrmions over a broad temperature range

  • 期刊论文

  • 发表日期：

    2025年10月3日

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  • Wei Li,
  • Sixu Wang,
  • Pai Peng,
  • Haojie Han,
  • Xinbo Wang,
  • Jing Ma,
  • Jianlin Luo,
  • Jun-Ming Liu,
  • Jing-Feng Li,
  • Ce-Wen Nan,
  • Qian Li

摘要

Ultrafast coherent control of electric dipoles using terahertz pulses provides a means to discover hidden phases of materials and potentially leads to applications in high-speed optoelectronic devices. Although this approach has been shown to be effective in incipient ferroelectrics only close to the phase transition temperatures, it relies on the soft phonon modes overlapping with the terahertz pulse bandwidth. Because of their emergent subterahertz collective dynamics, a fundamentally distinct and effective terahertz coupling mechanism can be envisaged in topological polar structures in PbTiO3/SrTiO3 superlattices. Here we demonstrate that polar skyrmions can be coherently driven into a hidden phase with transient macroscopic polarization, as probed using terahertz field-induced second-harmonic generation and optical Kerr effects. This ultrafast terahertz-driven phase transition is found to sustain across a broad temperature range of 4–470 K in a corresponding electric field required for equilibrium stability of skyrmions. Dynamical phase-field simulations reveal the correlation between the relaxation behaviour of the excited collective modes and the emergence of the polar phases. Our results manifest dynamical properties of topological polar structures, which could be technologically implemented given their flexibility in structure design and tunability under external electric fields.