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 ACa${}_2$Fe${}_4$As${}_4$F${}_2$ (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.

20 pages, 9 figures. Supplementary material included

References in corpus (30)

• Beyond Eliashberg superconductivity in MgB2: anharmonicity, two-phonon scattering, and multiple gaps
• Specific Heat of Mg ^{11}B_2
• Two-Band Superconductivity in MgB2
• London Penetration Depth in Iron - based Superconductors
• Thermal conductivity of single crystalline MgB_2
• Superfluid density and specific heat within self-consistent scheme for two-band superconductor
• Properties of the superconducting state in a two-band model
• Superconductivity in KCa${}_2$Fe${}_4$As${}_4$F${}_2$ with Separate Double Fe${}_2$As${}_2$ Layers
• Crystal Structure and Superconductivity at about 30 K in $A$Ca${}_2$Fe${}_4$As${}_4$F${}_2$ ($A$ = Rb, Cs)
• Neutron spin resonance in a quasi-two-dimensional iron-based superconductor
• Nodal multigap superconductivity in KCa${}_2$Fe${}_4$As${}_4$F${}_2$
• Two-gap superconductivity with line nodes in CsCa${}_2$Fe${}_4$As${}_4$F${}_2$
• Spectroscopic Evidence of Bilayer Splitting and Interlayer Pairing in an Iron Based Superconductor
• Charge Density Wave order and electron-phonon coupling in ternary superconductor Bi${}_2$Rh${}_3$Se${}_2$
• Ultrafast Optical Spectroscopy Evidence of Pseudogap and Electron-Phonon Coupling in an Iron-Based Superconductor KCa${}_2$Fe${}_4$As${}_4$F${}_2$
• Multigap nodeless superconductivity in CsCa2Fe4As4F2 probed by heat transport
• Complex state induced by impurities in multiband superconductors
• Single particle tunneling spectroscopy and superconducting gaps in layered iron based superconductor KCa${}_2$Fe${}_4$As${}_4$F${}_2$
• Band-selective clean- and dirty-limit superconductivity with nodeless gaps in the bilayer iron-based superconductor CsCa${}_2$Fe${}_4$As${}_4$F${}_2$
• Low temperature specific heat of 12442-type KCa_2Fe_4As_4F_2 single crystals
• Multi-band $s_{++}$ superconductivity in ${\text{V}}_3\text{Si}$ determined from the response to a controlled disorder
• Nodal multigap superconductivity in the anisotropic iron-based compound RbCa2Fe4As4F2
• Observation of a neutron spin resonance in the bilayered superconductor CsCa2Fe4As4F2
• Pseudogap and Strong Pairing Induced by Incipient and Shallow Bands in the Quasi-Two-Dimensional KCa${}_2$Fe${}_4$As${}_4$F${}_2$
• Evidence of electron interaction with an unidentified bosonic mode in superconductor CsCa${}_2$Fe${}_4$As${}_4$F${}_2$
• Fluctuated lattice-driven charge density wave far above the condensation temperature in kagome superconductor KV${}_3$Sb${}_5$
• A sample-position-autocorrection system with precision better than 1 \um~in angle-resolved photoemission experiments
• Unusual band splitting and superconducting gap evolution with sulfur substitution in FeSe
• Two characteristic contributions to the superconducting state of 2$H$-NbSe${}_2$
• Multiband superconductivity and a deep gap minimum from the specific heat in KCa${}_2$(Fe${}_{1-x}$Ni${}_x$)${}_4$As${}_4$F${}_2$ ($x$ = 0, 0.05, 0.13)