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Enhancement of the Superconducting Gap by Nesting in CaKFe4As4: A New High Temperature Superconductor

TitleEnhancement of the Superconducting Gap by Nesting in CaKFe4As4: A New High Temperature Superconductor
Publication TypeJournal Article
Year of Publication2016
AuthorsMou, DX, Kong, T, Meier, WR, Lochner, F, Wang, LL, Lin, QS, Wu, Y, Bud'ko, SL, Eremin, I, Johnson, DD, Canfield, PC, Kaminski, A
JournalPhysical Review Letters
Date Published12
Type of ArticleArticle
ISBN Number0031-9007
Accession NumberWOS:000391032500009
Keywordscs, fermi-surface, iron pnictides, pairing symmetry, physics, rb

n arsenides in the absence of doping or substitution. The Fermi surface consists of several hole and electron pockets that have a range of diameters. We find that the values of the superconducting gap are nearly isotropic (within the explored portions of the Brillouin zone), but are significantly different for each of the Fermi surface (FS) sheets. Most importantly, we find that the momentum dependence of the gap magnitude plotted across the entire Brillouin zone displays a strong deviation from the simple cos(k(x)) cos(k(y))functional form of the gap function, proposed by the scenario of Cooper pairing driven by a short range antiferromagnetic exchange interaction. Instead, the maximum value of the gap is observed on FS sheets that are closest to the ideal nesting condition, in contrast to previous observations in other ferropnictides. These results provide strong support for the multiband character of superconductivity in CaKFe4As4, in which Cooper pairing forms on the electron and the hole bands interacting via a dominant interband repulsive interaction, enhanced by band nesting.

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Complex States

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Materials Phase Transformations

Alternate JournalPhys. Rev. Lett.