Anti-chiral order and damped spin waves in the topological semi-metal Mn<sub>3</sub>Ge

 · Invited

Abstract

The kagome hexagonal compound Mn3Ge is a room temperature non-collinear antiferromagnet with anomalous transport properties associated with electronic Weyl nodes near the chemical potential. The coupling of its electronic transports with magnetic order presents important technological opportunities for which, I will describe our experimental efforts to understand the magnetism of Mn3Ge through neutron scattering techniques. Using polarized neutron diffraction, we show the magnetic order is a k=0 co-planar anti-chiral state with weak ferromagnetism described by a Γ9 irreducible representation with magnetization remarkably aligned perpendicular to an applied field. Using time-of-flight neutron spectroscopy, we find three collective excitations above distinct Γ-point anisotropy gaps. These can be modeled as the normal modes of an anti-chiral triangular spin plaquette where an out-of-plane mode anti-crosses an optical phonon near 15-18 meV. Away from the zone center, magnetic excitations form a broad maximum near 75 meV with a half-width at half maximum of 25(5) meV indicative of itinerant magnetism. We develop a field theory of spin waves, which accurately describes the long wavelength magnetic properties, and use it to determine an effective low energy spin hamitonian for Mn3Ge.

*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. DE-SC0019331. JG acknowledges support from the NSERC Postdoctoral Fellowship Program. CB and YC were supported by the Gordon and Betty Moore Foundation under GBM-4532.

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Presenters

  • Jonathan Gaudet

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

Authors

  • Jonathan Gaudet

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

  • Youzhe Chen

    • Johns Hopkins University

  • Sayak Dasgupta

    • Johns Hopkins University

  • Guy G Marcus

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

  • Jiao Lin

    • Oak Ridge National Laboratory
    • Spallation Neutron Source, Oak Ridge National Laboratory
    • Neutron Scattering Division, Oak Ridge National Laboratory

  • Yang Zhao

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

  • Wangchun Chen

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

  • 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

  • Muhammad Ikhlas

    • Institute for Solid State Physics, the University of Tokyo
    • ISSP, The University of Tokyo
    • Univ of Tokyo-Kashiwanoha
    • Institute for Solid State Physics, Univ of Tokyo-Kashiwanoha
    • ISSP, University of Tokyo

  • Taishi Chen

    • Institute for Solid State Physics, University of Tokyo
    • Univ of Tokyo-Kashiwanoha
    • Institute for Solid State Physics, Univ of Tokyo-Kashiwanoha

  • Takahiro Tomita

    • ISSP, The University of Tokyo
    • Univ of Tokyo-Kashiwanoha
    • Institute for Solid State Physics, Univ of Tokyo-Kashiwanoha

  • Oleg Tchernyshyov

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

  • Satoru Nakatsuji

    • Univ of Tokyo-Kashiwanoha
    • University of Tokyo
    • Institute for Solid State Physics, University of Tokyo
    • Institute for Solid State Physics, the University of Tokyo
    • Department of Physics, The University of Tokyo
    • Department of Physics, University of Tokyo
    • The Institute for Solid State Physics, The University of Tokyo
    • Institute for Solid State Physics, Univ of Tokyo-Kashiwanoha

  • 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