Mermin-Wagner physics, (H,T) phase diagram, and candidate quantum spin-liquid phase in the spin-1/2 triangular-lattice antiferromagnet Ba8CoNb6O24

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