Unique and unusual properties of layered ferrielectric CuInP2S6 - I. Theory

ORAL

Abstract

CuInP2S6 (CIPS) is a van der Waals layered ferrielectric with out-of-plane polarization and an ionic conductor. By combining density-functional-theory calculations and piezoelectric-force-microscopy experiments (next abstract by S. Neumayer et al.), we demonstrate that CIPS features a quadruple-well potential with four polarization states, corresponing1 to Cu atoms displacing within or just outside the CIPS layers. Under an applied voltage, the Cu atoms can go beyond the HP state and cross the vdW gaps, at which point the polarization aligns against the electric field.2 Further, because CIPS has two centrosymmetric planes, middle of layers and middle of vdW gaps, the polarization curve as a function of Cu displacements has a negative slope within the vdW gaps, signaling a regime of negative capacitance by a novel mechanism. This talk will describe the theoretical findings. It is followed by a talk (S. Neumayer et al.) on experimental validation. The unique and unusual properties of CIPS present new opportunities for novel applications.
1J. A. Brehm et al., Nat. Mater. 19, 43 (2020).
2S. M. Neumayer et al., Phy. Rev. Appl. 13, 064063 (2020).
3S. M. Neumayer et al., Adv. Energy Mater. 2020, online.

*Supported by US DOE, Office of Science, BES, MSTD. Computations at NERSC.

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Presenters

  • Lei Tao

    • Chinese Academy of Sciences

Authors

  • Lei Tao

    • Chinese Academy of Sciences

  • Sabine Neumayer

    • Oak Ridge National Laboratory
    • Oak Ridge National Lab

  • Andrew O'Hara

    • Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA
    • Department of Physics and Astronomy, Vanderbilt University
    • Department of Physics and Astronomy, Vanderbilt University, Nashville, TN
    • Vanderbilt University

  • John Brehm

    • Drexel University

  • Petro Maksymovych

    • Oak Ridge National Laboratory
    • Oak Ridge National Lab

  • Nina Balke

    • Oak Ridge National Laboratory
    • Oak Ridge National Lab

  • Sokrates T Pantelides

    • Department of Physics and Engineering, Vanderbilt University
    • Department of Physics and Astronomy, Vanderbilt Univ
    • Department of Physics and Astronomy, Vanderbilt University
    • Vanderbilt Univ
    • Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA
    • Institute of Physics, Chinese Academy of Sciences
    • Department of Physics and Astronomy & Department of Electrical Engineering and Computer Science, Vanderbilt University
    • Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN
    • Department of Electrical Engineering and Computer Science, Vanderbilt University
    • Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science, Vanderbilt University
    • Vanderbilt University