中国物理B ›› 2023, Vol. 32 ›› Issue (10): 107401-107401.doi: 10.1088/1674-1056/accd56

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First-principles study of moderate phonon-mediated pairing in high-pressure monoclinic phase of BiS2-based superconductors

Jie Cheng(程杰)1,†, Yu-Lan Cheng(程玉兰)2, Bin Li(李斌)1,‡, and Sheng-Li Liu(刘胜利)1   

  1. 1 School of Science, New Energy Technology Engineering Laboratory of Jiangsu Province, Nanjing University of Posts and Telecommunications, Nanjing 210023, China;
    2 College of Electronic and Optical Engineering&College of Flexible Electronics(Future Technology), Nanjing University of Posts and Telecommunications, Nanjing, 210023, China
  • 收稿日期:2023-02-12 修回日期:2023-04-07 接受日期:2023-04-17 出版日期:2023-09-21 发布日期:2023-09-21
  • 通讯作者: Jie Cheng, Bin Li E-mail:chengj@njupt.edu.cn;libin@njupt.edu.cn
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No. 12175107) and the Natural Science Foundation of Nanjing University of Posts and Telecommunications (Grant Nos. NY219087 and NY220038).

First-principles study of moderate phonon-mediated pairing in high-pressure monoclinic phase of BiS2-based superconductors

Jie Cheng(程杰)1,†, Yu-Lan Cheng(程玉兰)2, Bin Li(李斌)1,‡, and Sheng-Li Liu(刘胜利)1   

  1. 1 School of Science, New Energy Technology Engineering Laboratory of Jiangsu Province, Nanjing University of Posts and Telecommunications, Nanjing 210023, China;
    2 College of Electronic and Optical Engineering&College of Flexible Electronics(Future Technology), Nanjing University of Posts and Telecommunications, Nanjing, 210023, China
  • Received:2023-02-12 Revised:2023-04-07 Accepted:2023-04-17 Online:2023-09-21 Published:2023-09-21
  • Contact: Jie Cheng, Bin Li E-mail:chengj@njupt.edu.cn;libin@njupt.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No. 12175107) and the Natural Science Foundation of Nanjing University of Posts and Telecommunications (Grant Nos. NY219087 and NY220038).

摘要: Isotope effect on superconductive transition temperature ($T_{\rm c}$) is an essential indicator to examine whether the mechanism of superconductors is conventional. Unconventional isotope effect of BiS$_{2}$-based superconductors has been previously reported in ambient-pressure tetragonal phase. However, to comprehensively ascertain the nature of superconductivity, the investigation of BiS$_{2}$-based system in high-pressure structure is highly desirable. In this work, we carried out the first-principles calculations of phonon spectra and superconductivity in high-pressure monoclinic phase of LaO$_{0.5}$F$_{0.5}$BiS$_{2}$ with $^{32}$S and $^{34}$S, and observed that the corresponding isotope coefficient is $0.13 \le \alpha\le 0.20$. This value is much greater than that of BiS$_{2}$-based superconductors in ambient-pressure phase, but slightly smaller than that of conventional MgB$_{2}$. Taking into account the calculated $T_{\rm c}$ lower than experimental results, we finally conclude that the moderate phonon-mediated pairing plays a significant role in forming superconductivity of BiS$_{2}$-based system in high-pressure phase, moreover, the cooperative multiple paring interactions should also be considered.

关键词: BiS2-based superconductor, high pressure, isotope effect, phonon-mediated pairing

Abstract: Isotope effect on superconductive transition temperature ($T_{\rm c}$) is an essential indicator to examine whether the mechanism of superconductors is conventional. Unconventional isotope effect of BiS$_{2}$-based superconductors has been previously reported in ambient-pressure tetragonal phase. However, to comprehensively ascertain the nature of superconductivity, the investigation of BiS$_{2}$-based system in high-pressure structure is highly desirable. In this work, we carried out the first-principles calculations of phonon spectra and superconductivity in high-pressure monoclinic phase of LaO$_{0.5}$F$_{0.5}$BiS$_{2}$ with $^{32}$S and $^{34}$S, and observed that the corresponding isotope coefficient is $0.13 \le \alpha\le 0.20$. This value is much greater than that of BiS$_{2}$-based superconductors in ambient-pressure phase, but slightly smaller than that of conventional MgB$_{2}$. Taking into account the calculated $T_{\rm c}$ lower than experimental results, we finally conclude that the moderate phonon-mediated pairing plays a significant role in forming superconductivity of BiS$_{2}$-based system in high-pressure phase, moreover, the cooperative multiple paring interactions should also be considered.

Key words: BiS2-based superconductor, high pressure, isotope effect, phonon-mediated pairing

中图分类号:  (Effects of pressure)

  • 74.62.Fj
74.25.Kc (Phonons) 31.15.A- (Ab initio calculations) 74.70.-b (Superconducting materials other than cuprates)