Neutron spin resonance mode in iron-based superconductors

by Prof. Huiqian Luo (罗会仟) (Institute of Physics, Chinese Academy of Sciences)

Wednesday 14 Oct 2026, 10:00 → 11:00 Asia/Shanghai

Tsung-Dao Lee Institute/N4F-N400 - meeting room (Tsung-Dao Lee Institute)

Host: Prof. Vadim Grinenko  

Venue: TDLI Meeting Room N400

Tencent Meeting link: https://meeting.tencent.com/dm/P9Fef5Su8A4T

Meeting ID: 126412766, no password

 

Abstract:

High-Tc cuprates and iron-based superconductors (FeSCs) are speculated to have a common pairing mechanism based on spin fluctuations mediated Cooper pairing. Such picture is strongly supported by an extensively observed neutron spin resonance mode in the superconducting state [1]. In this talk, I would like to introduce our more than 10 year works on the spin resonance mode in iron-based superconductors. In the bilayer compound CaKFe4As₄ , we reveal a splitting resonance with two different modes with odd and even L-symmetries  due to the bilayer coupling[2], which similar to the bilayer cuprates like YBCO and Bi2212 [3]. In the 2D compound (Ca_0.85La_0.15)₁₀(Pt₃As₈)(Fe₂As₂)₅ , a resonance-like feature above Tc are found to like the spin excitations in the pseudogap state of cuprates [4]. Our polarized neutron scattering analysis suggests that the resonance is universally c-axis preferred in most FeSCs[5]. More interestingly, it is demonstrated that the c-axis dependence of the resonance can be scaled with the distance between two adjacent Fe-As layers (d) with a threshold of d = 6.7 A [6]. The in-plane dispersion of the resonance is very sensitive to the threshold [6-9]. For example, a downward dispersion of spin resonance is oberseved in slightly overdoped Ba_0.4K_0.6Fe₂As₂ with d = 6.74 A [10]. The behaviors of the spin resonance in FeSCs could be understood by a competing picture between the magnetically driven intra- and interlayer pairings, leading to a tunable and flexible superconductivity.

  

References：

[1] Pengcheng Dai, Rev. Mod. Phys. 87, 855 (2015).

[2] Tao Xie et al., Phys. Rev. Lett. 120, 267003 (2018).

[3] Y. Sidis et al.,  C. R. Phys. 8, 745 (2007).

[4] Zezong Li, Wenshan Hong, et al. arXiv:2501.08687.

[5] Chang Liu et al., Phys. Rev. Lett. 128, 137003 (2022).

[6] Wenshan Hong et al., Phys. Rev. B 107, 224514 (2023).

[7] Tao Xie et al., Chin. Phys. B 30, 127402 (2021).

[8] M. G. Kim et al., Phys. Rev. Lett. 110, 177002 (2013).

[9] Wenshan Hong et al., Phys. Rev. Lett. 125, 117002 (2020).

[10]    Yang Li, et al. Chin. Phys. Lett. 42, 067405 (2025).

 

Biography:

Huiqian Luo is a professor in condensed matter physics at the Institute of Physics, Chinese Academy of Sciences. He graduated at the Beijing Normal University in 2004, and got his PhD degree at the Institute of Physics, Chinese Academy of Sciences (IOP, CAS) in 2009. After that, he stayed at IOP, CAS and became an assistant professor, and an associate professor in 2012, then a full professor in 2022. His research interests focus on correlated electron materials such as iron-based superconductors, copper-oxide superconductors, heavy fermion compounds; spin-ladder materials, quantum spin liquid materials and magnetic topological materials, etc. He has published about 200 research papers with more than 5000 citations.