Campus Units

Chemistry, Materials Science and Engineering, Physics and Astronomy, Chemical and Biological Engineering, Ames Laboratory

Document Type

Article

Publication Version

Published Version

Publication Date

12-30-2016

Journal or Book Title

Physical Review Letters

Volume

117

First Page

277001-1

Last Page

277001-6

DOI

10.1103/PhysRevLett.117.277001

Abstract

We use high resolution angle resolved photoemission spectroscopy and density functional theory with measured crystal structure parameters to study the electronic properties of CaKFe4As4. In contrast to the related CaFe2As2 compounds, CaKFe4As4 has a high Tc of 35 K at stochiometric composition. This presents a unique opportunity to study the properties of high temperature superconductivity in the iron 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 cosðkxÞ cosðkyÞ 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.

Comments

This article is from Physical Review Letters 117, (2016): 277001-1, doi: 10.1103/PhysRevLett.117.277001. Posted with permission.

Copyright Owner

American Physical Society

Language

en

File Format

application/pdf

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