中国物理B ›› 2024, Vol. 33 ›› Issue (3): 37402-037402.doi: 10.1088/1674-1056/acf5d2

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Coexistence of antiferromagnetism and unconventional superconductivity in a quasi-one-dimensional flat-band system: Creutz lattice

Feng Xu(徐峰) and Lei Zhang(张磊)   

  1. School of Physics and Telecommunication Engineering, Shaanxi University of Technology, Hanzhong 723001, China
  • 收稿日期:2023-06-03 修回日期:2023-08-07 接受日期:2023-09-01 出版日期:2024-02-22 发布日期:2024-02-22
  • 通讯作者: Feng Xu E-mail:xufengxlx@snut.edu.cn
  • 基金资助:
    Project supported by the Natural Science Basic Research Program of Shaanxi (Program Nos. 2023KJXX-064 and 2021JQ-748), the National Natural Science Foundation of China (Grant Nos. 11804213 and 12174238), and Scientific Research Foundation of Shaanxi University of Technology (Grant No. SLGRCQD2006).

Coexistence of antiferromagnetism and unconventional superconductivity in a quasi-one-dimensional flat-band system: Creutz lattice

Feng Xu(徐峰) and Lei Zhang(张磊)   

  1. School of Physics and Telecommunication Engineering, Shaanxi University of Technology, Hanzhong 723001, China
  • Received:2023-06-03 Revised:2023-08-07 Accepted:2023-09-01 Online:2024-02-22 Published:2024-02-22
  • Contact: Feng Xu E-mail:xufengxlx@snut.edu.cn
  • Supported by:
    Project supported by the Natural Science Basic Research Program of Shaanxi (Program Nos. 2023KJXX-064 and 2021JQ-748), the National Natural Science Foundation of China (Grant Nos. 11804213 and 12174238), and Scientific Research Foundation of Shaanxi University of Technology (Grant No. SLGRCQD2006).

摘要: We study the coexistence of antiferromagnetism and unconventional superconductivity on the Creutz lattice which shows strictly flat bands in the noninteracting regime. The famous renormalized mean-field theory is used to deal with strong electron-electron repulsive Hubbard interaction in the effective low-energy t-J model, the superfluid weight of the unconventional superconducting state has been calculated via the linear response theory. An unconventional superconducting state with both spin-singlet and staggered spin-triplet pairs emerges beyond a critical antiferromagnetic coupling interaction, while antiferromagnetism accompanies this state. The superconducting state with only spin-singlet pairs is dominant with paramagnetic phase. The A phase is analogous to the pseudogap phase, which shows that electrons go to form pairs but do not cause a supercurrent. We also show the superfluid behavior of the unconventional superconducting state and its critical temperature. It is proven directly that the flat band can effectively raise the critical temperature of superconductivity. It is implementable to simulate and control strongly-correlated electrons' behavior on the Creutz lattice in the ultracold atoms experiment or other artificial structures. Our results may help the understanding of the interplay between unconventional superconductivity and magnetism.

关键词: flat-band unconventional superconductivity, antiferromagnetism, strong electron-electron interaction, superfluid weight

Abstract: We study the coexistence of antiferromagnetism and unconventional superconductivity on the Creutz lattice which shows strictly flat bands in the noninteracting regime. The famous renormalized mean-field theory is used to deal with strong electron-electron repulsive Hubbard interaction in the effective low-energy t-J model, the superfluid weight of the unconventional superconducting state has been calculated via the linear response theory. An unconventional superconducting state with both spin-singlet and staggered spin-triplet pairs emerges beyond a critical antiferromagnetic coupling interaction, while antiferromagnetism accompanies this state. The superconducting state with only spin-singlet pairs is dominant with paramagnetic phase. The A phase is analogous to the pseudogap phase, which shows that electrons go to form pairs but do not cause a supercurrent. We also show the superfluid behavior of the unconventional superconducting state and its critical temperature. It is proven directly that the flat band can effectively raise the critical temperature of superconductivity. It is implementable to simulate and control strongly-correlated electrons' behavior on the Creutz lattice in the ultracold atoms experiment or other artificial structures. Our results may help the understanding of the interplay between unconventional superconductivity and magnetism.

Key words: flat-band unconventional superconductivity, antiferromagnetism, strong electron-electron interaction, superfluid weight

中图分类号:  (Theories and models of superconducting state)

  • 74.20.-z
74.20.Mn (Nonconventional mechanisms) 74.25.Bt (Thermodynamic properties)