Seminar：Time-Reversal Symmetry Breaking Pairing in Iron-Chalcogenide Superconductors

Speaker: Cong-Jun Wu 

Westlake University

Time: 10:00am, Monday, June 21, 2021

Location: Room 242, East 4, Ziingang Campus

Abstract:

The symmetries of superconducting gap functions remain an important issue in iron-based superconductivity. Motivated by the recent angle-resolved photoemission spectroscopic measurements of iron-chalcogenide superconductors, we investigate the constraints to the gap function symmetries from the experimental measurements on the topological surface states. The surface Dirac cone has been observed to open a gap in the superconducting phase, it implies magnetization induced from time-reversal symmetry-breaking pairing via spin-orbit coupling. Based on the crystalline symmetry constraints on the Ginzburg-Landau free energy, the gap function symmetries are among the possibilities of A1g(u) ± iA2g(u), B1g(u) ± iB2g(u), or Eg(u) ± iEg(u). This time-reversal symmetry-breaking effect can exist in the normal state very close to Tc with the relative phase between two gap functions locked at ±π/2 . This study provides the connection between the gap function symmetries and topological properties of the surface state

References:

1. Meng Zeng, Lun-hui Hu, Hong-Ye Hu, Yi-Zhuang You, Congjun Wu, “Phase-fluctuation Induced Time-Reversal Symmetry Breaking Normal State”, arXiv:2102.06158.
2. N. Zaki, G. Gu, A. M. Tsvelik, Congjun Wu, P. D. Johnson, “Time Reversal Symmetry Breaking in the Fe-Chalcogenide Superconductors”, PNAS 118, e2007241118 (2021)
3. Lun-hui Hu, P. D. Johnson, Congjun Wu, “Pairing symmetry and topological surface state in iron-chalcogenide superconductors”, Phys. Rev. Research 2, 022021(R) .
4. Wei-cheng Lee, Shou-cheng Zhang, and Congjun Wu, “Pairing State with a Time-Reversal Symmetry Breaking in FeAs-Based Superconductors”, Phys. Rev. Lett. 102, 217002 (2009).

报告人简介：

吴从军，加利福尼亚大学圣迭戈分校物理系教授，美国物理学会会士。清华大学学士(1997)，北京大学硕士(2000)，斯坦福大学博士(2005)。曾获Sloan Research Fellowship和海外华人物理协会（现名全球华人物理学会）杰出青年科学家奖。在探索新物质状态和相应组织原则方面做出了杰出贡献，研究兴趣涵盖量子磁性、超导、拓扑状态、数学物理和量子蒙特卡洛模拟等方面。现已加入西湖大学，受聘物理学讲席教授。