Physics and Astronomy, Ames Laboratory
Journal or Book Title
Physical Review B
Measurements of the London penetration depth Δλ(T) and tunneling conductance in single crystals of the recently discovered stoichiometric iron-based superconductor CaKFe4As4 (CaK1144) show nodeless, two-effective-gap superconductivity with a larger gap of about 6–10 meV and a smaller gap of about 1–4 meV. Having a critical temperature Tc,onset≈35.8 K, this material behaves similar to slightly overdoped (Ba1−xKx)Fe2As2 (e.g., x=0.54,Tc≈34 K), a known multigap s± superconductor. We conclude that the superconducting behavior of stoichiometric CaK1144 demonstrates that two-gap s± superconductivity is an essential property of high-temperature superconductivity in iron-based superconductors, independent of the degree of substitutional disorder.
American Physical Society
Cho, Kyuil; Fente, A.; Teknowijoyo, S.; Tanatar, Makariy A.; Joshi, Kamal R.; Nusran, Naufer M.; Kong, Tai; Meier, William R.; Kaluarachchi, Udhara S.; Guillamon, I.; Suderow, H.; Bud’ko, Sergey L.; Canfield, Paul C.; and Prozorov, Ruslan, "Nodeless multiband superconductivity in stoichiometric single-crystalline CaKFe4 As4" (2017). Physics and Astronomy Publications. 530.