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Interplay between superconductivity and itinerant magnetism in underdoped Ba1−xKxFe2As2 (x = 0.2) probed by the response to controlled point-like disorder
Ames Laboratory Accepted Manuscripts
  • Ruslan Prozorov, Iowa State University and Ames Laboratory
  • Marcin Kończykowski, Institut Polytechnique
  • Makariy A. Tanatar, Iowa State University and Ames Laboratory
  • Hai-Hu Wen, Nanjing University
  • Rafael M. Fernandes, University of Minnesota
  • Paul C. Canfield, Iowa State University and Ames Laboratory
Publication Date
Ames Laboratory; Physics and Astronomy
Report Number
IS-J 9952
Journal Title
npj Quantum Materials

The response of superconductors to controlled introduction of point-like disorder is an important tool to probe their microscopic electronic collective behavior. In the case of iron-based superconductors, magnetic fluctuations presumably play an important role in inducing high-temperature superconductivity. In some cases, these two seemingly incompatible orders coexist microscopically. Therefore, understanding how this unique coexistence state is affected by disorder can provide important information about the microscopic mechanisms involved. In one of the most studied pnictide family, hole-doped Ba1−xKxFe2As2 (BaK122), this coexistence occurs over a wide range of doping levels, 0.16 ≲ x ≲ 0.25. We used relativistic 2.5 MeV electrons to induce vacancy-interstitial (Frenkel) pairs that act as efficient point-like scattering centers. Upon increasing dose of irradiation, the superconducting transition temperature Tc decreases dramatically. In the absence of nodes in the order parameter this provides a strong support for a sign-changing s± pairing. Simultaneously, in the normal state, there is a strong violation of the Matthiessen’s rule and a decrease (surprisingly, at the same rate as Tc) of the magnetic transition temperature Tsm, which indicates the itinerant nature of the long-range magnetic order. Comparison of the hole-doped BaK122 with electron-doped Ba(FexCo1−x)2As2 (FeCo122) with similar Tsm ~ 110 K, x = 0.02, reveals significant differences in the normal states, with no apparent Matthiessen’s rule violation above Tsm on the electron-doped side. We interpret these results in terms of the distinct impact of impurity scattering on the competing itinerant antiferromagnetic and s± superconducting orders.

DOE Contract Number(s)
Iowa State University Digital Repository, Ames IA (United States)
Citation Information
Ruslan Prozorov, Marcin Kończykowski, Makariy A. Tanatar, Hai-Hu Wen, et al.. "Interplay between superconductivity and itinerant magnetism in underdoped Ba1−xKxFe2As2 (x = 0.2) probed by the response to controlled point-like disorder" Vol. 4 (2019) p. 34
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