Spin dynamics in the skyrmion host lacunar spinel GaV<sub>4</sub>S<sub>8</sub>

ORAL

Abstract

In the lacunar spinel GaV4S8, the interplay of spin, charge, and orbital degrees of freedom results in a complex phase diagram that includes ferroelectric, orbitally ordered and Néel type skyrmion phases. Below 12.7 K, GaV4S8 exhibits a cycloidal state at zero field and a Néel type skyrmion spin structure with the application of field. To understand the physics driving the formation of these novel phases, we have carried out inelastic neutron scattering measurements on GaV4S8 above and below the ordering temperature of 12.7 K. Dispersive spin excitations with a zone boundary energy 5.65 meV are observed along the [100], and [110] directions within the magnetically ordered phase. The excitation spectrum softens along the third high symmetry direction, [111]. Using a Heisenberg model with near-neighbor exchange couplings and Dzyaloshinskii-Moria (DM) interactions, the excitation spectra are simulated. Simulation shows ferromagnetic inter-tetrahedral couplings with J= -0.69(3) meV. It is also observed that the DM interactions are around an order of magnitude weaker than the near-neighbor exchange interactions. A small and finite value of the DM interaction at 2 K provides evidence that the ground state of GaV4S8 is a cycloid below the ordering temperature in zero applied field.

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Presenters

  • Ganesh Pokharel

    • Physics, University of Tennessee
    • Physics and Astronomy, The University of Tennessee
    • Department of Physics & Astronomy, University of Tennessee, Knoxville
    • University of Tennessee
    • Department of Physics and Astronomy, The University of Tennessee
    • University of Tennessee, Knoxville

Authors

  • Ganesh Pokharel

    • Physics, University of Tennessee
    • Physics and Astronomy, The University of Tennessee
    • Department of Physics & Astronomy, University of Tennessee, Knoxville
    • University of Tennessee
    • Department of Physics and Astronomy, The University of Tennessee
    • University of Tennessee, Knoxville

  • Hasitha Suriya Arachchige

    • Physics and Astronomy, The University of Tennessee
    • Department of Physics & Astronomy, University of Tennessee, Knoxville
    • Department of Physics, University of Tennessee
    • University of Tennessee
    • Department of Physics and Astronomy, The University of Tennessee

  • Georg Ehlers

    • Neutron Technologies Division, OakRidge National Laboratory

  • Seunghwan Do

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

  • Matthew Stone

    • Oak Ridge National Lab
    • Neutron Scattering Division, Oak Ridge National Laboratory
    • Quantum Condensed Matter Div, Oak Ridge National Lab
    • Oak Ridge National Laboratory
    • Spallation Neutron Source, Oak Ridge National Laboratory
    • Neutron Scattering Division, Oak Ridge National Lab
    • Neutron Scattering Division, OakRidge National Laboratory

  • Mark D Lumsden

    • Neutron Scattering Division, Oak Ridge National Lab
    • Oak Ridge National Laboratory
    • Neutron Scattering Division, OakRidge National Laboratory

  • Hao Zhang

    • Department of Physics and Astronomy, University of Tennessee, Knoxville
    • Department of Physics and Astronomy, University of Tennessee
    • Department of Physics and Astronomy, The University of Tennessee

  • Cristian Batista

    • Physics and Astronomy, The University of Tennessee
    • Neutron Scattering Division and Shull-Wollan Center, Oak Ridge National Laboratory
    • Department of Physics and Astronomy, The University of Tennessee
    • University of Tennessee, Knoxville
    • Department of Physics and Astronomy, University of Tennessee, Knoxville
    • Department of Physics and Astronomy, University of Tennessee

  • Yiming Qiu

    • Center for Neutron Research, National Institute of Standards and Technology
    • National Institute of Standards and Technology
    • NIST
    • NIST Center for Neutron Research, National Institute of Standards and Technology

  • Randy Fishman

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

  • David Mandrus

    • Physics, University of Tennessee
    • Materials Science and Engineering, The University of Tennessee
    • Department of Materials Science & Engineering, University of Tennessee, Knoxville
    • The University of Tennesse, Knoxville
    • University of Tennessee
    • Department of Physics and Astronomy, University of Tennessee
    • Oak Ridge National Laboratory
    • Department of Materials Science and Engineering, University of Tennessee Knoxville
    • Department of Materials Science and Engineering, University of Tennessee
    • University of Tennessee, Knoxville
    • Material Science and Technology Division, Oak Ridge National Laboratory
    • Material Science and Technology Division, Oak Ridge National Lab

  • Andrew D Christianson

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