Decoupled interband pairing in a bilayer iron-based superconductor evidenced by ultrahigh-resolution angle-resolved photoemission spectroscopy
Shichong Wang, Yuanyuan Yang, Yang Li, Wenshan Hong, Huaxun Li, Shaofeng Duan, Lingxiao Gu, Haoran Liu, Jiongyu Huang, Jianzhe Liu, Dong Qian, Guanghan Cao, Huiqian Luo, Wentao Zhang
DOI 10.1103/vy32-xtt9 · Physical Review B
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Abstract
We present direct experimental evidence of a weakly coupled multiband superconducting state in the bilayer iron-based superconductor ACa2Fe4As4F2 (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.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| KCa2Fe4As4F2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 33.5 | Pressure not reported | onset |
| CsCa2Fe4As4F2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 30 | Pressure not reported | onset |
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