Topological spin excitations in a three-dimensional antiferromagnet

 · Invited

Abstract

The recent discovery of topological semimetals, which possess distinct electron-band crossing with non-trivial topological characteristics in the bulk, has stimulated intense research interest. By extending the notion of symmetry-protected band crossing into one of the simplest magnetic groups, namely by including the symmetry of time-reversal followed by space-inversion, we predict the existence of topological magnon-band crossing in three-dimensional antiferromagnets [1]. The crossing may take the forms of Dirac points and nodal lines, in the presence and absence, respectively, of the conservation of the total spin along the ordered moments. In a concrete example of a Heisenberg spin model for a "spin-web" compound, Cu3TeO6, we theoretically demonstrate the presence of Dirac magnons over a wide parameter range using linear spin-wave approximation [1]. Inelastic neutron scattering experiments have been carried out to detect the bulk magnon-band crossing in a single-crystal sample [2]. The highly interconnected nature of the spin-1/2 lattice suppresses quantum fluctuations and facilitates our experimental observation, leading to remarkably clean experimental data and very good agreement with the linear spin-wave calculations. The predicted topological magnon Dirac points are confirmed. Further studies will be discussed, including determination of non-collinear spin canting in the ground state with neutron diffraction, and search for topological magnon surface states with inelastic neutron scattering.

[1] K. Li et al., Phys. Rev. Lett. 119, 247202 (2017).
[2] W. Yao et al., Nat. Phys. 14, 1011 (2018).

*This work is supported by the NSFC and the MOST of China.

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Presenters

  • Yuan Li

    • Internationan Center for Quantum Materials, Peking University
    • Peking University
    • International Center for Quantum Materials, Peking University
    • School of Physics, Peking University

Authors

  • Weiliang Yao

    • Internationan Center for Quantum Materials, Peking University
    • Peking University

  • Chenyuan Li

    • Internationan Center for Quantum Materials, Peking University
    • Peking University

  • Lichen Wang

    • Internationan Center for Quantum Materials, Peking University
    • International Center for Quantum Materials, Peking University

  • Shangjie Xue

    • Internationan Center for Quantum Materials, Peking University

  • Yang Dan

    • Internationan Center for Quantum Materials, Peking University

  • Kazuki Iida

    • Comprehensive Research Organization for Science and Society, Japan
    • Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS)
    • Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society

  • Kazuya Kamazawa

    • Comprehensive Research Organization for Science and Society, Japan
    • Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society

  • Kangkang Li

    • Institute of Physics, Chinese Academy of Sciences

  • Jiangping Hu

    • Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
    • Institute of Physics, Chinese Academy of Sciences
    • Chinese Academy of Sciences
    • Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China

  • Chen Fang

    • Chinese Academy of Sciences
    • Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
    • Institute of Physics, Chinese Academy of Sciences
    • Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
    • Institute of physics, Chinese Academy of Sciences

  • Yuan Li

    • Internationan Center for Quantum Materials, Peking University
    • Peking University
    • International Center for Quantum Materials, Peking University
    • School of Physics, Peking University