Nodeless multiband superconductivity in stoichiometric single-crystalline CaKFe4As4

Kyuil Cho; A. Fente; S. Teknowijoyo; M. A. Tanatar; K. R. Joshi; N. M. Nusran; T. Kong; W. R. Meier; U. Kaluarachchi; I. Guillamón; H. Suderow; S. L. Bud'ko; P. C. Canfield; R. Prozorov

doi:10.1103/PhysRevB.95.100502

Nodeless multiband superconductivity in stoichiometric single-crystalline CaKFe4As4

Kyuil Cho, A. Fente, S. Teknowijoyo, M. A. Tanatar, K. R. Joshi, N. M. Nusran, T. Kong, W. R. Meier, U. Kaluarachchi, I. Guillamón, H. Suderow, S. L. Bud'ko, P. C. Canfield, R. Prozorov

DOI 10.1103/PhysRevB.95.100502 · Physical Review B

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Abstract

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.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
CaKFe4As4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	35.8	Pressure not reported	onset
CaKFe4As4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	35.8	Pressure not reported	onset
CaKFe4As4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	35.8	Pressure not reported	onset
Ba0.46K0.54Fe2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	34	Pressure not reported	unknown
KFe2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	3.6	Pressure not reported	unknown
LiFeAs Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	18	Pressure not reported	unknown
LiFeP Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	5	Pressure not reported	unknown
LaFePO Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	6	Pressure not reported	unknown
FeSe Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	9	Pressure unresolved	unknown
FeS Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	5	Pressure not reported	unknown
BaFe2(As0.70P0.30)2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	30	Pressure not reported	unknown
Ba0.65K0.35Fe2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	39	Pressure not reported	unknown