Letter | Published:

Evidence for a spinon Fermi surface in a triangular-lattice quantum-spin-liquid candidate

Nature volume 540, pages 559562 (22 December 2016) | Download Citation

Abstract

A quantum spin liquid is an exotic quantum state of matter in which spins are highly entangled and remain disordered down to zero temperature. Such a state of matter is potentially relevant to high-temperature superconductivity and quantum-information applications, and experimental identification of a quantum spin liquid state is of fundamental importance for our understanding of quantum matter. Theoretical studies have proposed various quantum-spin-liquid ground states1,2,3,4, most of which are characterized by exotic spin excitations with fractional quantum numbers (termed ‘spinons’). Here we report neutron scattering measurements of the triangular-lattice antiferromagnet YbMgGaO4 that reveal broad spin excitations covering a wide region of the Brillouin zone. The observed diffusive spin excitation persists at the lowest measured energy and shows a clear upper excitation edge, consistent with the particle–hole excitation of a spinon Fermi surface. Our results therefore point to the existence of a quantum spin liquid state with a spinon Fermi surface in YbMgGaO4, which has a perfect spin-1/2 triangular lattice as in the original proposal4 of quantum spin liquids.

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Acknowledgements

We thank D. Lee, S. Li, Y. Lu, X. Wang and, especially, J.-W. Mei for discussions, and F. Song for assistance with magnetic susceptibility measurements. This work was supported by the National Key R&D Program of the MOST of China (grant number 2016YFA0300203), the Ministry of Science and Technology of China (Program 973: 2015CB921302), and the National Natural Science Foundation of China (grant number 91421106). Y.-D.L. and G.C. were supported by the Thousand Youth Talent Program of China. Q.M.Z. was supported by the NSF of China and the Ministry of Science and Technology of China (grant number 2016YFA0300504). A portion of this research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.

Author information

Affiliations

  1. State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China

    • Yao Shen
    • , Hongliang Wo
    • , Shoudong Shen
    • , Bingying Pan
    • , Qisi Wang
    • , Yiqing Hao
    • , Gang Chen
    •  & Jun Zhao
  2. School of Computer Science, Fudan University, Shanghai 200433, China

    • Yao-Dong Li
  3. Department of Physics, Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, China

    • Yuesheng Li
    •  & Qingming Zhang
  4. ISIS Facility, Rutherford Appleton Laboratory, STFC, Chilton, Didcot OX11 0QX, UK

    • H. C. Walker
  5. Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble Cedex 9, France

    • P. Steffens
    •  & M. Boehm
  6. Helmholtz-Zentrum Berlin für Materialien und Energie, D-14109 Berlin, Germany

    • D. L. Quintero-Castro
  7. NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA

    • L. W. Harriger
  8. Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393, USA

    • M. D. Frontzek
  9. Neutron Scattering Laboratory, China Institute of Atomic Energy, Beijing 102413, China

    • Lijie Hao
    •  & Siqin Meng
  10. Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China

    • Qingming Zhang
  11. Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China

    • Qingming Zhang
    • , Gang Chen
    •  & Jun Zhao
  12. Center for Field Theory and Particle Physics, Fudan University, Shanghai 200433, China

    • Gang Chen

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Contributions

J.Z. and G.C. planned the project. Y.S., H.W. and S.S. synthesized the sample. Y.S. and Y.H. characterized the sample with the help of Y.L. and Q.Z. Y.S., H.W., S.S., B.P., Q.W., H.C.W., P.S. and J.Z. carried out the neutron experiments with experimental assistance from M.B., D.L.Q.-C., L.W.H., L.H., M.D.F. and S.M. J.Z. and Y.S. analysed the data. Y.-D.L. and G.C. provided the theoretical explanation and calculations. J.Z., G.C., Y.S. and Y.-D.L. wrote the paper. All authors provided comments on the paper.

Corresponding authors

Correspondence to Gang Chen or Jun Zhao.

Reviewer Information Nature thanks C. Rüegg and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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DOI

https://doi.org/10.1038/nature20614

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