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XFEL Ultrafast

  • Tuesday 2
  • 10:50
  • - 11:20
  • 1402
  • Talk # 3
  • Session # 1

Polarization density waves in SrTiO3

  • 1- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, USA.
  • 2- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA, USA.

Presenting Author:

  • Mariano
  • Trigo

mtrigo@slac.stanford.edu

Ultrafast optical excitation can drive materials into novel states that cannot be achieved under equilibrium conditions. Strong terahertz (THz) pulses have been shown to induce transient ferroelectricity in the quantum paraelectric SrTiO3 (1-2), opening possibilities for ultrafast, reversible structural control. This behavior differs markedly from equilibrium observations, which suggest an incipient phase characterized by spatially modulated polarization at low temperatures (3–6), underscoring the necessity for microscopic structural characterization of the nonequilibrium ferroelectric state. In this presentation, I will discuss our investigation of quantum paraelectric SrTiO3 using THz excitation combined with diffuse x-ray scattering, a technique that allows us to probe collective excitations of the lattice (phonons) with wavelengths of nanometers. We present a new methodology for probing inversion symmetry breaking, which uncovers hybrid polar-acoustic modes exhibiting pronounced softening at characteristic wavelengths of tens of nanometers. These findings point to a structural instability in SrTiO3 featuring spatially-modulated polarization that differs from uniform ferroelectricity (5,6). Our observations (7) underscore the critical role of momentum-resolved measurements of fluctuations and offer fresh understanding of the microscopic nature of quantum paraelectric materials.

References

[1] X. Li, T. Qiu, J. Zhang, E. Baldini, J. Lu, A. M. Rappe, and K. A. Nelson, Science 364, 1079 (2019).

[2] T. F. Nova, A. S. Disa, M. Fechner, and A. Cavalleri, Science 364, 1075 (2019).

[3] M. J. Coak, C. R. S. Haines, C. Liu, S. E. Rowley, G. G. Lonzarich, and S. S. Saxena, Proceedings of the National Academy of Sciences 117, 12707 (2020).

[4]  S. E. Rowley, L. J. Spalek, R. P. Smith, M. P. M. Dean, M. Itoh, J. F. Scott, G. G. Lonzarich, and S. S. Saxena, Nature Physics 10, 367 (2014).

[5] G. G. Guzmán-Verri, C. H. Liang, and P. B. Littlewood, Physical Review Letters 131, 046801 (2023).

[6] B. Fauqué, P. Bourges, A. Subedi, K. Behnia, B. Baptiste, B. Roessli, T. Fennell, S. Raymond, and P. Steffens, Physical Review B 106, L140301 (2022).

[7] Orenstein, G., Krapivin, V., Huang, Y. et al. Observation of polarization density waves in SrTiO3. Nat. Phys. 21, 961 (2025).