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Quantum disordered ground state in the triangular-lattice magnet NaRuO2

Nature Physics volume 19, pages 943–949 (2023)Cite this article

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Abstract

It has long been hoped that spin liquid states might be observed in materials that realize the triangular-lattice Hubbard model. However, weak spin–orbit coupling and other small perturbations often induce conventional spin freezing or magnetic ordering. Sufficiently strong spin–orbit coupling, however, can renormalize the electronic wavefunction and induce anisotropic exchange interactions that promote magnetic frustration. Here we show that the cooperative interplay of spin–orbit coupling and correlation effects in the triangular-lattice magnet NaRuO2 produces an inherently fluctuating magnetic ground state. Despite the presence of a charge gap, we find that low-temperature spin excitations generate a metal-like term in the specific heat and a continuum of excitations in neutron scattering, reminiscent of spin liquid states previously found in triangular-lattice organic magnets. Further cooling produces a crossover into a different, highly disordered spin state whose dynamic spin autocorrelation function reflects persistent fluctuations. These findings establish NaRuO2 as a cousin to organic, Heisenberg spin liquid compounds with a low-temperature crossover in quantum disorder.

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Fig. 1: Lattice and electronic band structures of NaRuO2.
Fig. 2: Electrical transport, magnetic susceptibility and heat capacity data characterizing the low-temperature properties of NaRuO2.
Fig. 3: Inelastic neutron scattering data collected on NaRuO2.
Fig. 4: Muon spin relaxation data and analysis.

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Data availability

The data that support the findings of this study are available at https://doi.org/10.25349/D9R626.

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Acknowledgements

We thank R. Valentí and L. Hozoi for sharing preliminary ab initio calculations of the magnetic exchange interactions. This work was supported by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences, under award no. DE-SC0017752 (S.D.W., B.R.O. and P.M.S.). Work by L.B. was supported by the DOE, Office of Science, Basic Energy Sciences, under award no. DE-FG02-08ER46524. Part of this work is based on experiments performed at the Swiss Muon Source SμS, Paul Scherrer Institute, Villigen, Switzerland. R.S. and A.H. acknowledge support from the National Science Foundation (NSF) through Enabling Quantum Leap: Convergent Accelerated Discovery Foundries for Quantum Materials Science, Engineering and Information (Q-AMASE-i), Quantum Foundry at the University of California, Santa Barbara (DMR-1906325). A portion of this research used the resources at the High Flux Isotope Reactor and Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. Use of the Advanced Photon Source at Argonne National Laboratory was supported by the US DOE, Office of Science, Office of Basic Energy Sciences, under contract no. DE-AC02-06CH11357. We thank the National Institute of Standards and Technology for access to their neutron facilities. Certain commercial equipment, instruments or materials are identified in this document. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the products identified are necessarily the best available for the purpose.

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Author notes

  1. These authors contributed equally: Brenden R. Ortiz, Paul M. Sarte.

Authors and Affiliations

  1. Materials Department, University of California, Santa Barbara, Santa Barbara, CA, USA

    Brenden R. Ortiz, Paul M. Sarte, Alon Hendler Avidor, Aurland Hay, Ram Seshadri & Stephen D. Wilson

  2. Department of Physics, Boston College, Chestnut Hill, MA, USA

    Eric Kenney & Michael J. Graf

  3. Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA

    Alexander I. Kolesnikov, Daniel M. Pajerowski, Adam A. Aczel & Keith M. Taddei

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

    Craig M. Brown

  5. Chemical and Biomolecular Engineering, University of Delaware, Newark, DE, USA

    Craig M. Brown

  6. Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, Villigen, Switzerland

    Chennan Wang

  7. Kavli Institute for Theoretical Physics, University of California, Santa Barbara, Santa Barbara, CA, USA

    Leon Balents

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Contributions

S.D.W. wrote the manuscript with input from all the co-authors. B.R.O., P.M.S. and A.H. synthesized the material and performed the resistivity, magnetization and neutron scattering measurements. A.H. and R.S. performed the ab initio density functional theory calculations. E.K., M.J.G. and C.W. performed the muon spin relaxation measurements. A.I.K., C.M.B., D.M.P., K.M.T. and A.H.A. performed the neutron scattering measurements. L.B. provided theoretical insights into modelling the material. All the authors participated in the planning and discussions of experiments.

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Correspondence to Stephen D. Wilson.

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Supplementary Figs. 1–8 and Table 1.

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Ortiz, B.R., Sarte, P.M., Avidor, A.H. et al. Quantum disordered ground state in the triangular-lattice magnet NaRuO2. Nat. Phys. 19, 943–949 (2023). https://doi.org/10.1038/s41567-023-02039-x

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