The governing role of interlayer chemical bonding in polar properties of the van-der-Waals ferroelectric CuInP<sub>2</sub>S<sub>6</sub>

ORAL

Abstract


Copper indium thiophosphate (CuInP2S6) is a van-der-Waals (vdW) layered crystal that is ferrielectric below room temperature. It has unusual properties, including a negative longitudinal piezoelectric coefficient whose atomistic origin remains unknown. In this talk, we present the results of density functional theory calculations which show that the potential energy for Cu displacement away from the centrosymmetric position has two distinct minima in each longitudinal direction instead of the usual one, with stable positions within the layer as well as in the vdW gap. The two minima correspond to two structural phases with distinct polarizations, which is corroborated by piezoresponse force microscopy experimental data. The anharmonicity of the potential governing Cu displacements yields a negative piezoresponse in one of the phases. At the same time, the potential is strongly influenced by strain and the corresponding width of the vdW gap, rendering CuInP2S6 a rare example of a uniaxial non-zero-polarization multi-well ferroelectric, with new potential for both fundamental studies and prospective applications.

*U.S. DoE grant DE-FG02-09ER46554.
Basic Energy Sciences, US Department of Energy. Laboratory Directed R&D at ORNL

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Presenters

  • John Brehm

    • Department of Physics and Astronomy, Vanderbilt University
    • Vanderbilt University

Authors

  • John Brehm

    • Department of Physics and Astronomy, Vanderbilt University
    • Vanderbilt University

  • Marius Chyasnavichus

    • Oak Ridge National Lab

  • Sabine Neumayer

    • Oak Ridge National Lab

  • Nina Balke

    • Oak Ridge National Lab
    • Oak Ridge National Laboratory

  • Michael Susner

    • Air Force Research Laboratory
    • Air Force Research Laboratory, Wright-Patterson Air Force Base

  • Michael A McGuire

    • Oak Ridge National Lab
    • Materials Science and Technology Division, Oak Ridge National Laboratory
    • Oak Ridge National Laboratory

  • Panchapakesan Ganesh

    • Center for Nanophase Materials Sciences, Oak Ridge National Laboratory
    • Oak Ridge National Lab
    • Oak Ridge National Laboratory
    • Center for Nanophase Materials and Sciences, Oak Ridge National Laboratory

  • Petro Maksymovych

    • Oak Ridge National Lab

  • Sokrates T Pantelides

    • Department of Physics and Astronomy, Vanderbilt University
    • Vanderbilt University
    • physics, Vanderbilt University
    • Physics, Vanderbilt University
    • Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science, Vanderbilt University
    • Dept. of Physics and Astronomy, Vanderbilt University, USA