Pseudospin-triplet pairing in iron-chalcogenide superconductors

Journal Article · 04 January 2024 · Communications Physics

DOI: https://doi.org/10.1038/s42005-023-01495-4 · OSTI ID:2278883

Zeng, Meng ; Xu, Dong-Hui; Wang, Zi-Ming; Hu, Lun-Hui ; Zhang, Fu-Chun

Abstract Understanding the pairing symmetry is a crucial theoretical aspect in the study of unconventional superconductivity for interpreting experimental results. Here we study superconductivity of electron systems with both spin and pseudospin-1/2 degrees of freedom. By solving linearized gap equations, we derive a weak coupling criterion for the even-parity spin-singlet pseudospin-triplet pairing. It can generally mix with the on-site s -wave pairing since both of them belong to the same symmetry representation ( A _{1 g} ) and their mixture could naturally give rise to anisotropic intra-band pairing gap functions with or without nodes. This may directly explain why some of the iron-chalcogenide superconductors are fully gapped (e.g. FeSe thin film) and some have nodes (e.g. LaFePO and LiFeP). We also find that the anisotropy of gap functions can be enhanced when the principal rotation symmetry is spontaneously broken in the normal state such as nematicity, and the energetic stabilization of pseudospin-triplet pairings indicates the coexistence of nematicity and superconductivity. This could be potentially applied to bulk FeSe, where gap anisotropy has been experimentally observed.

• Research Organization: Pennsylvania State Univ., University Park, PA (United States)
• Sponsoring Organization: USDOE; USDOE Office of Science (SC)
• Grant/Contract Number: SC0019064
• OSTI ID: 2278883
• Journal Information: Communications Physics, Journal Name: Communications Physics Journal Issue: 1 Vol. 7; ISSN 2399-3650
• Publisher: Nature Publishing GroupCopyright Statement
• Country of Publication: United Kingdom
• Language: English