Observation of a ubiquitous three-dimensional superconducting gap function in optimally-doped Ba\(_{0.6}\)K\(_{0.4}\)Fe\(_2\)As\(_2\)

• Published in: arXiv.org
• Main Authors: Y -M Xu, Y -B Huang, X -Y Cui, Razzoli, E, Radovic, M, Shi, M, G -F Chen, Zheng, P, N -L Wang, P -C Dai, J -P Hu, Wang, Z, Ding, H
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 08.03.2011
• Subjects: Anisotropy; Antiferromagnetism; Coupling (molecular); Electronic structure; Energy gap; Fermi surfaces; Group 5A compounds; High temperature superconductors; Interlayers; Iron; Photoelectric emission; Superconductivity; Superconductors; Variations
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1006.3958

The iron-pnictide superconductors have a layered structureformed by stacks of FeAs planes from which the superconductivity originates. Given the multiband and quasi three-dimensional \cite{3D_SC} (3D) electronic structure of these high-temperature superconductors, knowledge of the quasi-3D superconducting (SC) gap is essential for understanding the superconducting mechanism. By using the \KZ-capability of angle-resolved photoemission, we completely determined the SC gap on all five Fermi surfaces (FSs) in three dimensions on \BKFAOP samples. We found a marked \KZ dispersion of the SC gap, which can derive only from interlayer pairing. Remarkably, the SC energy gaps can be described by a single 3D gap function with two energy scales characterizing the strengths of intralayer \(\Delta_1\) and interlayer \(\Delta_2\) pairing. The anisotropy ratio \(\Delta_2/\Delta_1\), determined from the gap function, is close to the c-axis anisotropy ratio of the magnetic exchange coupling \(J_c/J_{ab}\) in the parent compound \cite{NeutronParent}. The ubiquitous gap function for all the 3D FSs reveals that pairing is short-ranged and strongly constrain the possible pairing force in the pnictides. A suitable candidate could arise from short-range antiferromagnetic fluctuations.