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Title: Enhancement of the superconducting gap by nesting in CaKFe 4 As 4 : A new high temperature superconductor

We use high resolution angle resolved photoemission spectroscopy and density functional theory with measured crystal structure parameters to study the electronic properties of CaKFe 4As 4. In contrast to the related CaFe 2As 2 compounds, CaKFe 4As 4 has a high T c 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 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.more » Finally, these results provide strong support for the multiband character of superconductivity in CaKFe 4As 4, in which Cooper pairing forms on the electron and the hole bands interacting via a dominant interband repulsive interaction, enhanced by band nesting.« less
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [3] ;  [1] ;  [1] ;  [2] ;  [1] ;  [1] ;  [1]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States)
  2. Ruhr-Univ. Bochum, Bochum (Germany)
  3. Ames Lab., Ames, IA (United States)
Publication Date:
Report Number(s):
IS-J-9162; IS-J-9203
Journal ID: ISSN 0031-9007; PRLTAO; TRN: US1701075
Grant/Contract Number:
AC02-07CH11358; ER463/8; ER463/8-1; 57316180; GBMF4411
Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 117; Journal Issue: 27; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1347412
Alternate Identifier(s):
OSTI ID: 1338133; OSTI ID: 1347744