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# Field-tunable quantum disordered ground state in the triangular-lattice antiferromagnet NaYbO2

## Abstract

Antiferromagnetically coupled S = 1/2 spins on an isotropic triangular lattice are the paradigm of frustrated quantum magnetism, but structurally ideal realizations are rare. Here, we investigate NaYbO2, which hosts an ideal triangular lattice of effective Jeff = 1/2 moments with no inherent site disorder. No signatures of conventional magnetic order appear down to 50 mK, strongly suggesting a quantum spin liquid ground state. We observe a two-peak specific heat and a nearly quadratic temperature dependence, in agreement with expectations for a two-dimensional Dirac spin liquid. Application of a magnetic field strongly perturbs the quantum disordered ground state and induces a clear transition into a collinear ordered state, consistent with a long-predicted up–up–down structure for a triangular-lattice XXZ Hamiltonian driven by quantum fluctuations. The observation of spin liquid signatures in zero field and quantum-induced ordering in intermediate fields in the same compound demonstrates an intrinsically quantum disordered ground state. We conclude that NaYbO2 is a model, versatile platform for exploring spin liquid physics with full tunability of field and temperature.

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## Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request. Neutron data were collected on the BT-1 diffractometer and the Disk Chopper Spectrometer at the NIST Center for Neutron Research.

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## Acknowledgements

This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under award DE-SC0017752 (S.D.W. and M.B.). M.B. acknowledges partial support by the National Science Foundation Graduate Research Fellowship Program under grant no. 1650114. Work by L.B. and C.L. was supported by the DOE, Office of Science, Basic Energy Sciences under award no. DE-FG02-08ER46524. Identification of commercial equipment does not imply recommendation or endorsement by NIST.

## Author information

Authors

### Contributions

M.B., S.D.W., C.L. and L.B. wrote the manuscript. M.B. and S.D.W. analysed experiment data and planned experiments. M.J.G. and E.K. performed susceptibility measurements. M.B. and T.H. performed heat capacity and magnetization measurements. C.L. and L.B. performed theoretical analysis of the material. C.B. performed the neutron diffraction measurements, and M.B. and N.P.B. performed inelastic neutron-scattering experiments. M.S., M.K., Y.L. and M.B. performed electron spin resonance measurements. M.B. and L.P. synthesized the materials.

### Corresponding author

Correspondence to Stephen D. Wilson.

## Ethics declarations

### Competing interests

The authors declare no competing interests.

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## Supplementary information

### Supplementary Information

Supplementary text, Figs. 1–5 and references.

## Rights and permissions

Reprints and Permissions

Bordelon, M.M., Kenney, E., Liu, C. et al. Field-tunable quantum disordered ground state in the triangular-lattice antiferromagnet NaYbO2. Nat. Phys. 15, 1058–1064 (2019). https://doi.org/10.1038/s41567-019-0594-5

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