Soft Polar-Acoustic Excitations Reveal an Incipient Modulated Phase in SrTiO3

ORAL

Abstract

Enhanced fluctuations are one of the hallmarks of continuous phase transitions, however in some cases these fluctuations inhibit long-range order down to zero temperature. Even when not fully ordered, the associated elementary excitations of the system inherit properties of the underlying ``hidden order''. Here we study quantum paraelectric SrTiO3, a quintessential example of such frustrated orders. We use ultrafast x-ray scattering at a free electron laser, together with a novel approach to probe inversion symmetry breaking using intense terahertz pulses, to resolve the polar excitations of SrTiO3. We find that the relevant low-energy excitations at low temperature are polar-acoustic and particularly soft at the tens of nanometer lengthscale. These soft polar-acoustic modes indicate precursor fluctuations of an incipient polar state in which the polarization and strain are spatially modulated, and is distinct from the known homogeneous ferroelectric state. Our results provide a glimpse into potential modulated phases of SrTiO3 and highlight the importance of probing fluctuations with atomic resolution both in equilibrium and at ultrafast timescales.

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Presenters

  • Gal Orenstein

    • Stanford

Authors

  • Gal Orenstein

    • Stanford

  • Viktor Krapivin

    • Stanford University

  • Yijing Huang

    • Stanford University

  • Zhuquan Zhang

    • Massachusetts Institute of Technology
    • MIT

  • Gilberto De La Pena

    • SLAC - Natl Accelerator Lab

  • Ryan A Duncan

    • Stanford University

  • Jade Stanton

    • Stanford University
    • Stanford

  • Samuel W Teitelbaum

    • Arizona State University

  • Hasan Yavas

    • SLAC

  • Takahiro Sato

    • SLAC National Accelerator Laboratory

  • Matthias C Hoffmann

    • SLAC National Accelerator Laboratory
    • SLAC NATIONAL ACCELERATOR LABORATORY
    • SLAC
    • Linac Coherent Light Source, SLAC National Accelerator Laboratory

  • Patrick L Kramer

    • SLAC National Accelerator Laboratory
    • SLAC

  • Alfred Q Baron

    • RIKEN SPring-8 Center

  • Andrea Cavalleri

    • Max Planck Institute for the Structure & Dynamics of Matter

  • Riccardo Comin

    • Massachusetts Institute of Technology
    • MIT

  • Mark P Dean

    • Brookhaven National Laboratory

  • Ankit S Disa

    • Cornell University

  • Michael Först

    • Max Planck Institute for the Structure & Dynamics of Matter)
    • MPSD
    • Max Planck Institute for the Structure and Dynamics of Matter

  • Steven L Johnson

    • ETH Zurich

  • Matteo Mitrano

    • Harvard University

  • David A Reis

    • Stanford PULSE Institute

  • Diling Zhu

    • SLAC - Natl Accelerator Lab

  • Keith A Nelson

    • MIT

  • Mariano Trigo

    • SLAC - Natl Accelerator Lab