中国物理B ›› 2020, Vol. 29 ›› Issue (5): 57506-057506.doi: 10.1088/1674-1056/ab889b

所属专题: Virtual Special Topic — Magnetism and Magnetic Materials

• SPECIAL TOPIC—Recent advances in thermoelectric materials and devices • 上一篇    下一篇

Tunable deconfined quantum criticality and interplay of different valence-bond solid phases

Bowen Zhao(赵博文), Jun Takahashi, Anders W. Sandvik   

  1. 1 Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA;
    2 Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
  • 收稿日期:2020-03-18 修回日期:2020-04-02 出版日期:2020-05-05 发布日期:2020-05-05
  • 通讯作者: Anders W. Sandvik E-mail:sandvik@bu.edu
  • 基金资助:
    Project supported by the NSF under Grant No. DMR-1710170 and by a Simons Investigator Grant.

Tunable deconfined quantum criticality and interplay of different valence-bond solid phases

Bowen Zhao(赵博文)1, Jun Takahashi2,1, Anders W. Sandvik1,2   

  1. 1 Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA;
    2 Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
  • Received:2020-03-18 Revised:2020-04-02 Online:2020-05-05 Published:2020-05-05
  • Contact: Anders W. Sandvik E-mail:sandvik@bu.edu
  • Supported by:
    Project supported by the NSF under Grant No. DMR-1710170 and by a Simons Investigator Grant.

摘要: We use quantum Monte Carlo simulations to study an S=1/2 spin model with competing multi-spin interactions. We find a quantum phase transition between a columnar valence-bond solid (cVBS) and a Néel antiferromagnet (AFM), as in the scenario of deconfined quantum-critical points, as well as a transition between the AFM and a staggered valence-bond solid (sVBS). By continuously varying a parameter, the sVBS-AFM and AFM-cVBS boundaries merge into a direct sVBS-cVBS transition. Unlike previous models with putative deconfined AFM-cVBS transitions, e.g., the standard J-Q model, in our extended J-Q model with competing cVBS and sVBS inducing terms the transition can be tuned from continuous to first-order. We find the expected emergent U(1) symmetry of the microscopically Z4 symmetric cVBS order parameter when the transition is continuous. In contrast, when the transition changes to first-order, the clock-like Z4 fluctuations are absent and there is no emergent higher symmetry. We argue that the confined spinons in the sVBS phase are fracton-like. We also present results for an SU(3) symmetric model with a similar phase diagram. The new family of models can serve as a useful tool for further investigating open questions related to deconfined quantum criticality and its associated emergent symmetries.

关键词: quantum phase transitions, deconfined quantum criticality, quantum spin systems, quantum Monte Carlo simulations

Abstract: We use quantum Monte Carlo simulations to study an S=1/2 spin model with competing multi-spin interactions. We find a quantum phase transition between a columnar valence-bond solid (cVBS) and a Néel antiferromagnet (AFM), as in the scenario of deconfined quantum-critical points, as well as a transition between the AFM and a staggered valence-bond solid (sVBS). By continuously varying a parameter, the sVBS-AFM and AFM-cVBS boundaries merge into a direct sVBS-cVBS transition. Unlike previous models with putative deconfined AFM-cVBS transitions, e.g., the standard J-Q model, in our extended J-Q model with competing cVBS and sVBS inducing terms the transition can be tuned from continuous to first-order. We find the expected emergent U(1) symmetry of the microscopically Z4 symmetric cVBS order parameter when the transition is continuous. In contrast, when the transition changes to first-order, the clock-like Z4 fluctuations are absent and there is no emergent higher symmetry. We argue that the confined spinons in the sVBS phase are fracton-like. We also present results for an SU(3) symmetric model with a similar phase diagram. The new family of models can serve as a useful tool for further investigating open questions related to deconfined quantum criticality and its associated emergent symmetries.

Key words: quantum phase transitions, deconfined quantum criticality, quantum spin systems, 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.))