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Multiple Coulomb phase in the fluoride pyrochlore CsNiCrF6

Nature Physicsvolume 15pages6066 (2019) | Download Citation


The Coulomb phase is an idealized state of matter whose properties are determined by factors beyond conventional considerations of symmetry, including global topology, conservation laws and emergent order. Theoretically, Coulomb phases occur in ice-type systems such as water ice and spin ice; in dimer models; and in certain spin liquids. However, apart from ice-type systems, more general experimental examples are very scarce. Here we study the partly disordered material CsNiCrF6 and show that this material is a multiple Coulomb phase with signature correlations in three degrees of freedom: charge configurations, atom displacements and spin configurations. We use neutron and X-ray scattering to separate these correlations and to determine the magnetic excitation spectrum. Our results show how the structural and magnetic properties of apparently disordered materials may inherit, and be dictated by, a hidden symmetry—the local gauge symmetry of an underlying Coulomb phase.

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The experimental data and their supplementary information, analyses and computer codes that support the plots within this paper and the findings of this study are available from the corresponding author upon reasonable request.

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We thank R. Stewart, M. Green and B. Fåk for discussions, J. Chalker for reading and commenting on the manuscript, and X. Thonon for support of cryogenics at the ILL. M.R. was supported by the Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, grant no. 200021_140862. This work is based on experiments performed at the Institut Laue-Langevin, Grenoble, France; the Swiss spallation neutron source SINQ, Paul Scherrer Institut, Villigen, Switzerland; and the Swiss Light Source, Paul Scherrer Institut.

Author information


  1. Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, Villigen PSI, Switzerland

    • T. Fennell
    • , M. Ruminy
    •  & O. Zaharko
  2. School of Divinity, University of Edinburgh, New College, Edinburgh, UK

    • M. J. Harris
  3. Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA

    • S. Calder
  4. Institut Laue-Langevin, Grenoble, France

    • M. Boehm
    • , P. Steffens
    •  & M.-H. Lemée-Cailleau
  5. Swiss Light Source, Paul Scherrer Institut, Villigen PSI, Switzerland

    • A. Cervellino
  6. London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London, UK

    • S. T. Bramwell


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T.F., M.J.H., S.C., M.B., P.S. and S.T.B. carried out inelastic neutron scattering experiments. T.F., M.-H.L.-C. and O.Z. carried out neutron diffraction experiments. M.R. and A.C. carried out X-ray diffraction experiments. T.F. analysed all data and made calculations. T.F., M.J.H. and S.T.B. wrote the paper in collaboration with all other authors.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to T. Fennell.

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    Supplementary Text, Figures 1–3, Table 1

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