Magnon spectrum of the chiral ferrimagnet Cu<sub>2</sub>OSeO<sub>3</sub>: a coarse-grained approach

ORAL

Abstract

We report a comprehensive neutron scattering study of low energy magnetic excitations in the breathing pyrochlore helimagnetic Cu2OSeO3. Fully documenting the four lowest energy modes that leave the ferrimagnetic configuration of the "strong tetrahedra" intact (\hbar ω<13 meV), we find quadratic dispersion at the Γ point for energies above 0.2 meV with any gap less than 0.19 meV, two doublets separated by 1.6(2) meV at the R point, and a bounded continuum at the X point. Our constrained rigid spin cluster model relates these features to Dzyaloshinskii-Moriya(DM) interactions and the incommensurate helical ground state. Combining conventional spin wave theory with a spin cluster form-factor accurately reproduces the measured equal time structure factor through multiple Brillouin zones. An effective spin Hamiltonian describing the complex anisotropic inter-cluster interactions is obtained.

*This work was supported as part of the Institute for Quantum Matter, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award No. DESC0019331. Collin Broholm and Jonas Kindervater were supported by the Gordon and Betty Moore Foundation under the EPQS program grant number GBMF-4532.

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Presenters

  • Yi Luo

    • Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University

Authors

  • Yi Luo

    • Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University

  • Guy G Marcus

    • Johns Hopkins University
    • Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University

  • Benjamin Trump

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

  • Jonas Kindervater

    • Johns Hopkins University
    • Physics Department, Technical University of Munich, Germany
    • Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University

  • 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

  • Tyrel McQueen

    • Johns Hopkins University
    • Chemistry, Johns Hopkins Univ
    • Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University

  • Oleg Tchernyshyov

    • Johns Hopkins University
    • Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University

  • Collin Leslie Broholm

    • The Johns Hopkins University
    • Johns Hopkins University
    • Physics and Astronomy, Johns Hopkins University
    • Physics, The Johns Hopkins University
    • Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University