Mermin-Wagner physics, (H,T) phase diagram, and candidate quantum spin-liquid phase in the spin-1/2 triangular-lattice antiferromagnet Ba<sub>8</sub>CoNb<sub>6</sub>O<sub>24</sub>

ORAL

Abstract

Ba8CoNb6O24 presents a system whose Co2+ ions have an effective spin 1/2 and construct a regular triangular-lattice antiferromagnet (TLAFM) with a very large interlayer spacing, ensuring purely two-dimensional character. We exploit this ideal realization to perform a detailed experimental analysis of the S=1/2 TLAFM, which is one of the keystone models in frustrated quantum magnetism. We find strong low-energy spin fluctuations and no magnetic ordering, but a diverging correlation length down to 0.1 K, indicating a Mermin-Wagner trend towards zero-temperature order. Below 0.1 K, however, our low-field measurements show an unexpected magnetically disordered state, which is a candidate quantum spin liquid. We establish the (H,T) phase diagram, mapping in detail the quantum fluctuation corrections to the available theoretical analysis. These include a strong upshift in field of the maximum ordering temperature, qualitative changes to both low- and high-field phase boundaries, and an ordered regime apparently dominated by the collinear "up-up-down" state. Ba8CoNb6O24 therefore offers fresh input for the development of theoretical approaches to the field-induced quantum phase transitions of the S=1/2 Heisenberg TLAFM.

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Presenters

  • Tao Xiang

    • Institute of Physics, The Chinese Academy of Sciences
    • Institute of Physics, Chinese Academy of Scienes (CAS)
    • Institute of Physics, Chinese Academy of Sciences

Authors

  • Tao Xiang

    • Institute of Physics, The Chinese Academy of Sciences
    • Institute of Physics, Chinese Academy of Scienes (CAS)
    • Institute of Physics, Chinese Academy of Sciences

  • Bruce Normand

    • Neutrons and Muons Research Division, Paul Scherrer Institute
    • Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute

  • Yi Cui

    • Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China

  • Jia Dai

    • Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China

  • Long Ma

    • High Magnetic Field Laboratory, Chinese Academy of Sciences

  • Zheng Zhang

    • State Key Laboratory of Surface Physics and Laboratory of Advanced Materials, Department of Physics, Fudan University

  • Shiyan Li

    • University of Sherbrooke
    • Fudan Univ
    • State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University
    • State Key Laboratory of Surface Physics and Laboratory of Advanced Materials, Department of Physics, Fudan University
    • Fudan University

  • Graeme Luke

    • McMaster University
    • Physics and Astronomy, McMaster University
    • Department of Physics and Astronomy, McMaster Univ
    • Department of Physics and Astronomy, McMaster University
    • Physics and Astronomy, McMaster Univ
    • MacMaster University
    • Physics, McMaster University
    • McMaster Univ

  • Weiqiang Yu

    • Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China
    • Department of Physics, Renmin Univ of China