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Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO3

  • Author(s): Chen, F
  • Zhu, Y
  • Liu, S
  • Qi, Y
  • Hwang, HY
  • Brandt, NC
  • Lu, J
  • Quirin, F
  • Enquist, H
  • Zalden, P
  • Hu, T
  • Goodfellow, J
  • Sher, MJ
  • Hoffmann, MC
  • Zhu, D
  • Lemke, H
  • Glownia, J
  • Chollet, M
  • Damodaran, AR
  • Park, J
  • Cai, Z
  • Jung, IW
  • Highland, MJ
  • Walko, DA
  • Freeland, JW
  • Evans, PG
  • Vailionis, A
  • Larsson, J
  • Nelson, KA
  • Rappe, AM
  • Sokolowski-Tinten, K
  • Martin, LW
  • Wen, H
  • Lindenberg, AM
  • et al.
Abstract

© 2016 American Physical Society. The dynamical processes associated with electric field manipulation of the polarization in a ferroelectric remain largely unknown but fundamentally determine the speed and functionality of ferroelectric materials and devices. Here we apply subpicosecond duration, single-cycle terahertz pulses as an ultrafast electric field bias to prototypical BaTiO3 ferroelectric thin films with the atomic-scale response probed by femtosecond x-ray-scattering techniques. We show that electric fields applied perpendicular to the ferroelectric polarization drive large-amplitude displacements of the titanium atoms along the ferroelectric polarization axis, comparable to that of the built-in displacements associated with the intrinsic polarization and incoherent across unit cells. This effect is associated with a dynamic rotation of the ferroelectric polarization switching on and then off on picosecond time scales. These transient polarization modulations are followed by long-lived vibrational heating effects driven by resonant excitation of the ferroelectric soft mode, as reflected in changes in the c-axis tetragonality. The ultrafast structural characterization described here enables a direct comparison with first-principles-based molecular-dynamics simulations, with good agreement obtained.

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