中国物理B ›› 2021, Vol. 30 ›› Issue (6): 67505-067505.doi: 10.1088/1674-1056/abf3b8

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Emergent O(4) symmetry at the phase transition from plaquette-singlet to antiferromagnetic order in quasi-two-dimensional quantum magnets

Guangyu Sun(孙光宇)1,2, Nvsen Ma(马女森)3,1, Bowen Zhao(赵博文)4, Anders W. Sandvik4,1,†, and Zi Yang Meng(孟子杨)1,5,‡   

  1. 1 Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;
    2 School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China;
    3 School of Physics, Key Laboratory of Micro-Nano Measurement-Manipulation and Physics, Beihang University, Beijing 100191, China;
    4 Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA;
    5 Department of Physics and HKU-UCAS Joint Institute of Theoretical and Computational Physics, The University of Hong Kong, Hong Kong, China
  • 收稿日期:2021-03-02 修回日期:2021-03-30 接受日期:2021-03-31 出版日期:2021-05-18 发布日期:2021-06-01
  • 通讯作者: Anders W. Sandvik, Zi Yang Meng E-mail:sandvik@bu.edu;zymeng@iphy.ac.cn
  • 基金资助:
    GYU, NVM, and ZYM acknowledge the support from the RGC of Hong Kong SAR China (Grant Nos. GRF 17303019 and 17301420), the National Key Research and Development Program of China (Grant No. 2016YFA0300502), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB33000000). N. M acknowledges support from the National Natural Science Foundation of China (Grant No. 12004020). AWS was supported by the NSF (Grant No. DMR-1710170) and by the Simons Foundation (Grant No. 511064).

Emergent O(4) symmetry at the phase transition from plaquette-singlet to antiferromagnetic order in quasi-two-dimensional quantum magnets

Guangyu Sun(孙光宇)1,2, Nvsen Ma(马女森)3,1, Bowen Zhao(赵博文)4, Anders W. Sandvik4,1,†, and Zi Yang Meng(孟子杨)1,5,‡   

  1. 1 Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;
    2 School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China;
    3 School of Physics, Key Laboratory of Micro-Nano Measurement-Manipulation and Physics, Beihang University, Beijing 100191, China;
    4 Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA;
    5 Department of Physics and HKU-UCAS Joint Institute of Theoretical and Computational Physics, The University of Hong Kong, Hong Kong, China
  • Received:2021-03-02 Revised:2021-03-30 Accepted:2021-03-31 Online:2021-05-18 Published:2021-06-01
  • Contact: Anders W. Sandvik, Zi Yang Meng E-mail:sandvik@bu.edu;zymeng@iphy.ac.cn
  • Supported by:
    GYU, NVM, and ZYM acknowledge the support from the RGC of Hong Kong SAR China (Grant Nos. GRF 17303019 and 17301420), the National Key Research and Development Program of China (Grant No. 2016YFA0300502), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB33000000). N. M acknowledges support from the National Natural Science Foundation of China (Grant No. 12004020). AWS was supported by the NSF (Grant No. DMR-1710170) and by the Simons Foundation (Grant No. 511064).

摘要: Recent experiments[Guo et al., Phys. Rev. Lett. 124 206602 (2020)] on thermodynamic properties of the frustrated layered quantum magnet SrCu2(BO3)2—the Shastry-Sutherland material—have provided strong evidence for a low-temperature phase transition between plaquette-singlet and antiferromagnetic order as a function of pressure. Further motivated by the recently discovered unusual first-order quantum phase transition with an apparent emergent O(4) symmetry of the antiferromagnetic and plaquette-singlet order parameters in a two-dimensional "checkerboard J-Q" quantum spin model[Zhao et al., Nat. Phys. 15 678 (2019)], we here study the same model in the presence of weak inter-layer couplings. Our focus is on the evolution of the emergent symmetry as the system crosses over from two to three dimensions and the phase transition extends from strictly zero temperature in two dimensions up to finite temperature as expected in SrCu2(BO3)2. Using quantum Monte Carlo simulations, we map out the phase boundaries of the plaquette-singlet and antiferromagnetic phases, with particular focus on the triple point where these two ordered phases meet the paramagnetic phase for given strength of the inter-layer coupling. All transitions are first-order in the neighborhood of the triple point. We show that the emergent O(4) symmetry of the coexistence state breaks down clearly when the interlayer coupling becomes sufficiently large, but for a weak coupling, of the magnitude expected experimentally, the enlarged symmetry can still be observed at the triple point up to significant length scales. Thus, it is likely that the plaquette-singlet to antiferromagnetic transition in SrCu2(BO3)2 exhibits remnants of emergent O(4) symmetry, which should be observable due to additional weakly gapped Goldstone modes.

关键词: quantum phase transitions, quantum spin systems, emergent symmetry, quantum Monte Carlo simulations

Abstract: Recent experiments[Guo et al., Phys. Rev. Lett. 124 206602 (2020)] on thermodynamic properties of the frustrated layered quantum magnet SrCu2(BO3)2—the Shastry-Sutherland material—have provided strong evidence for a low-temperature phase transition between plaquette-singlet and antiferromagnetic order as a function of pressure. Further motivated by the recently discovered unusual first-order quantum phase transition with an apparent emergent O(4) symmetry of the antiferromagnetic and plaquette-singlet order parameters in a two-dimensional "checkerboard J-Q" quantum spin model[Zhao et al., Nat. Phys. 15 678 (2019)], we here study the same model in the presence of weak inter-layer couplings. Our focus is on the evolution of the emergent symmetry as the system crosses over from two to three dimensions and the phase transition extends from strictly zero temperature in two dimensions up to finite temperature as expected in SrCu2(BO3)2. Using quantum Monte Carlo simulations, we map out the phase boundaries of the plaquette-singlet and antiferromagnetic phases, with particular focus on the triple point where these two ordered phases meet the paramagnetic phase for given strength of the inter-layer coupling. All transitions are first-order in the neighborhood of the triple point. We show that the emergent O(4) symmetry of the coexistence state breaks down clearly when the interlayer coupling becomes sufficiently large, but for a weak coupling, of the magnitude expected experimentally, the enlarged symmetry can still be observed at the triple point up to significant length scales. Thus, it is likely that the plaquette-singlet to antiferromagnetic transition in SrCu2(BO3)2 exhibits remnants of emergent O(4) symmetry, which should be observable due to additional weakly gapped Goldstone modes.

Key words: quantum phase transitions, quantum spin systems, emergent symmetry, quantum Monte Carlo simulations

中图分类号:  (Quantized spin models, including quantum spin frustration)

  • 75.10.Jm
64.70.Tg (Quantum phase transitions) 75.40.Mg (Numerical simulation studies) 75.30.Kz (Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.))