Signatures of ultrafast reversal of excitonic order in Ta<sub>2</sub>NiSe<sub>5</sub>

ORAL

Abstract

In the presence of electron-phonon coupling, an excitonic insulator can harbor two degenerate ground states described by an Ising-type order parameter. Starting from a microscopic Hamiltonian, we derive the equations of motion for the electronic and structural order parameters in the excitonic insulator Ta2NiSe5. We show that the excitonic order can be controllably reversed with appropriate laser excitation sequences. Using a combination of theory and coherent phonon spectroscopy measurements, we report evidence of such reversal in Ta2NiSe5. Our work expands the field of ultrafast order parameter control beyond conventional spin and charge ordered materials.

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Presenters

  • Honglie Ning

    • Department of Physics, California Institute of Technology

Authors

  • Honglie Ning

    • Department of Physics, California Institute of Technology

  • Omar Mehio

    • Department of Physics, California Institute of Technology
    • California Institute of Technology

  • Michael Buchhold

    • Department of Physics, California Institute of Technology

  • Takashi Kurumaji

    • Massachusetts Institute of Technology MIT
    • Department of Physics, Massachusetts Institute of Technology

  • Gil Refael

    • Department of Physics, California Institute of Technology

  • Joseph Checkelsky

    • Massachusetts Institute of Technology, Department of Physics, Cambridge, MA, USA
    • Massachusetts Institute of Technology MIT
    • Department of Physics, Massachusetts Institute of Technology
    • Massachusetts Institute of Technology
    • Physics, Massachusetts Institute of Technology

  • David Hsieh

    • Department of Physics, California Institute of Technology
    • California Institute of Technology
    • Caltech
    • Physics, California Institute of Technology