Decoupled interband pairing in a bilayer iron-based superconductor evidenced by ultrahigh-resolution ARPES
Abstract
We present direct experimental evidence of a weakly coupled multiband superconducting state in the bilayer iron-based superconductor ACaFeAsF (A = K, Cs) via ultrahigh-resolution angle-resolved photoemission spectroscopy (ARPES). Remarkably, the K-containing compound exhibits two distinct transition temperatures, corresponding to two separate sets of bilayer-split bands, as evidenced by temperature-dependent superconducting gap and spectral weight near the Fermi energy, while its Cs counterpart displays conventional single transition behavior. These experimental observations are well described by the weakly coupled two-band model of Eilenberger theory, which identifies suppressed interband pairing interactions between the bilayer-split bands as the key mechanism. By exploring quantum phenomena in the weak-coupling limit within a multiband system, our findings pave the way for engineering exotic superconductivity via band-selective pairing control.
Cite
@article{arxiv.2601.07380,
title = {Decoupled interband pairing in a bilayer iron-based superconductor evidenced by ultrahigh-resolution ARPES},
author = {Shichong Wang and Yuanyuan Yang and Yang Li and Wenshan Hong and Huaxun Li and Shaofeng Duan and Lingxiao Gu and Haoran Liu and Jiongyu Huang and Jianzhe Liu and Dong Qian and Guanghan Cao and Huiqian Luo and Wentao Zhang},
journal= {arXiv preprint arXiv:2601.07380},
year = {2026}
}
Comments
20 pages, 9 figures. Supplementary material included