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A magnetic continuum in the cobalt-based honeycomb magnet BaCo2(AsO4)2

Nature Materials volume 22, pages 58–63 (2023)Cite this article

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Abstract

Quantum spin liquids (QSLs) are topologically ordered states of matter that host fractionalized excitations. A particular route towards a QSL is via strongly bond-dependent interactions on the hexagonal lattice. A number of Ru- and Ir-based candidate Kitaev QSL materials have been pursued, but all have appreciable non-Kitaev interactions. Using time-domain terahertz spectroscopy, we observed a broad magnetic continuum over a wide range of temperatures and fields in the honeycomb cobalt-based magnet BaCo2(AsO4)2, which has been proposed to be a more ideal version of a Kitaev QSL. Applying an in-plane magnetic field of ~0.5 T suppresses the magnetic order, and at higher fields, applying the field gives rise to a spin-polarized state. Under a 4 T magnetic field that was oriented principally out of plane, a broad magnetic continuum was observed that may be consistent with a field-induced QSL. Our results indicate BaCo2(AsO4)2 is a promising QSL candidate.

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Fig. 1: The broad magnetic continuum investigated by time-domain terahertz spectroscopy.
Fig. 2: The magnetic excitations with in-plane magnetic field and phase diagram.
Fig. 3: The evolution of the magnetic excitations with primarily out-of-plane field.

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Data availability

The data that support the findings of this study are present in the paper and/or in the Supplementary Information, and are deposited in the Zenodo repository: https://doi.org/10.5281/zenodo.7026702. Additional data related to the paper are available from the corresponding author upon reasonable request.

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Acknowledgements

This research was supported as part of the Institute for Quantum Matter, an Energy Frontier Research Center funded by the US Department of Energy’s Basic Energy Sciences programme under DE-SC0019331. N.P.A. had additional support from the Quantum Materials programme at the Canadian Institute for Advanced Research. We thank P. Chauhan and A. Legros for critical comments on this manuscript and H.-Y. Kee, G. Khaliullin and H. Liu for helpful conversations.

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Authors and Affiliations

  1. Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA

    Xinshu Zhang, Yuanyuan Xu, T. Halloran, C. Broholm, N. Drichko & N. P. Armitage

  2. Department of Chemistry, Princeton University, Princeton, NJ, USA

    Ruidan Zhong & R. J. Cava

  3. NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, USA

    C. Broholm

  4. Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD, USA

    C. Broholm

  5. Canadian Institute for Advanced Research, Toronto, Ontario, Canada

    N. P. Armitage

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  1. Xinshu Zhang
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Contributions

X.Z. performed the terahertz experiments and analysed the data. R.Z. and R.J.C. grew the single crystals. Y.X. and N.D. performed the Raman spectroscopy. T.H. and C.B. performed the magnetization experiments. X.Z. and N.P.A. prepared the first draft, and all authors contributed to writing the manuscript.

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Correspondence to N. P. Armitage.

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Zhang, X., Xu, Y., Halloran, T. et al. A magnetic continuum in the cobalt-based honeycomb magnet BaCo2(AsO4)2. Nat. Mater. 22, 58–63 (2023). https://doi.org/10.1038/s41563-022-01403-1

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