Title
Competing pairing interactions responsible for the large upper critical field in a stoichiometric iron-based superconductor CaKFe4As4
Publication Date
4-1-2020
Department
Ames Laboratory; Physics and Astronomy
Campus Units
Ames Laboratory, Physics and Astronomy
OSTI ID+
1615930
Report Number
IS-J 10199
DOI
10.1103/PhysRevB.101.134502
Journal Title
Physical Review B
Volume Number
101
Issue Number
13
First Page
134502
Abstract
The upper critical field of multiband superconductors is an important quantity that can reveal details about the nature of the superconducting pairing. Here we experimentally map out the complete upper-critical-field phase diagram of a stoichiometric superconductor, CaKFe4As4, up to 90T for different orientations of the magnetic field and at temperatures down to 4.2K. The upper critical fields are extremely large, reaching values close to ∼3Tc at the lowest temperature, and the anisotropy decreases dramatically with temperature, leading to essentially isotropic superconductivity at 4.2K. We find that the temperature dependence of the upper critical field can be well described by a two-band model in the clean limit with band-coupling parameters favoring intraband over interband interactions. The large Pauli paramagnetic effects together with the presence of the shallow bands is consistent with the stabilization of an FFLO state at low temperatures in this clean superconductor.
DOE Contract Number(s)
EP/I004475/1; EP/EP/I017836/1; EP/N01085X/1; EP/M020517/1; AC02-07CH11358; GBMF4411
Language
en
Publisher
Iowa State University Digital Repository, Ames IA (United States)
