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Creators/Authors contains: "Lee, Hyeon Jun"

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  1. Free, publicly-accessible full text available March 1, 2025
  2. null (Ed.)
  3. Abstract

    Above‐bandgap femtosecond optical excitation of a ferroelectric/dielectric BaTiO3/CaTiO3superlattice leads to structural responses that are a consequence of the screening of the strong electrostatic coupling between the component layers. Time‐resolved X‐ray free‐electron laser diffraction shows that the structural response to optical excitation includes a net lattice expansion of the superlattice consistent with depolarization‐field screening driven by the photoexcited charge carriers. The depolarization‐field‐screening‐driven expansion is separate from a photoacoustic pulse launched from the bottom electrode on which the superlattice is epitaxially grown. The distribution of diffracted intensity of superlattice X‐ray reflections indicates that the depolarization‐field‐screening‐induced strain includes a photoinduced expansion in the ferroelectric BaTiO3and a contraction in CaTiO3. The magnitude of expansion in BaTiO3layers is larger than the contraction in CaTiO3. The difference in the magnitude of depolarization‐field‐screening‐driven strain in the BaTiO3and CaTiO3components can arise from the contribution of the oxygen octahedral rotation patterns at the BaTiO3/CaTiO3interfaces to the polarization of CaTiO3. The depolarization‐field‐screening‐driven polarization reduction in the CaTiO3layers points to a new direction for the manipulation of polarization in the component layers of a strongly coupled ferroelectric/dielectric superlattice.

     
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