Quantum fluctuations in an easy axis spin-1/2 triangular lattice antiferromagnet

ORAL

Abstract

In the search for quantum entangled states of matter, materials with triangular lattices of antiferromagnetically interacting magnetic ions remain a focal point. We report the magnetic phase diagram and excitations of a spin-½ easy axis triangular lattice antiferromagnet, K2Co(SeO3)2. While there is no sharp specific heat anomaly in zero field, there is a prominent magnetization plateau phase at 1/3 of the saturation magnetization [1]. For 0.96 T<B<21.2 T this plateau phase is marked by a second order phase boundary, which however, terminates at (T,B)=(4.4(2) K, 0.9(1) T). Neutron diffraction reveals persistent two-dimensional √3×√3<!--[if gte msEquation 12]> style='mso-bidi-font-style:normal'>√3×√3 magnetic order for T<12 K and B=0 T that can be described as an antiferromagnetic honeycomb lattice. Neutron spectroscopy uncovers low energy continuum scattering at zero field that we associate with the quantum disordered spins within honeycombs. In the plateau phase these spins become magnetized and the system supports coherent spin waves. From their dispersion relation we infer the spin Hamiltonian, which features nearest neighbor interactions with Jz=29.95(3) meV and Jxy=0.26(2) meV.

*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. A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-2128556* and the State of Florida. CB was supported by the Gordon and Betty Moore foundation under GBMF9456.

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Publication: [1] Zhong, R., Guo, S., & Cava, R. J. (2020). Frustrated magnetism in the layered triangular lattice materials K2Co(SeO3)2 and Rb2Co(SeO3)2. Physical Review Materials, 4(8). https://doi.org/10.1103/PhysRevMaterials.4.084406

Presenters

  • Alireza Ghasemi

    • Johns Hopkins University

Authors

  • Alireza Ghasemi

    • Johns Hopkins University

  • Tong Chen

    • Johns Hopkins University

  • Junyi Zhang

    • Johns Hopkins University

  • Liyu Shi

    • Johns Hopkins University

  • Eun Sang Choi

    • National High Magnetic Field Laboratory
    • National High Magnetic Field Lab, Tallahassee, Florida
    • NHMFL
    • MagLab
    • Florida State University
    • National High Magnetic Field Laboratory, Florida State University

  • Minseong Lee

    • Los Alamos National Lab

  • Yiqing Hao

    • Oak Ridge National Laboratory

  • Huibo Cao

    • Oak Ridge National Laboratory

  • Barry Winn

    • Oak Ridge National Laboratory
    • Oak Ridge National Laboratory, Oak Ridge, Tennessee
    • ORNL

  • Marcelo Jaime

    • Los Alamos Natl Lab
    • Physikalisch Technische Bundesanstalt

  • Xianghan Xu

    • Princeton University

  • Ruidan Zhong

    • Princeton University

  • Robert J Cava

    • Princeton University

  • Peter N Armitage

    • Johns Hopkins University

  • Collin L Broholm

    • John Hopkins University
    • Johns Hopkins University