Slope of the upper critical field at Tc in two-band superconductors with nonmagnetic disorder: s++ superconductivity in Ba1−xKxFe2As2

R. Prozorov; V. G. Kogan; M. Kończykowski; M. A. Tanatar

doi:10.1103/PhysRevB.109.024506

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Slope of the upper critical field at Tc in two-band superconductors with nonmagnetic disorder: s++ superconductivity in Ba1−xKxFe2As2

R. Prozorov, V. G. Kogan, M. Kończykowski, M. A. Tanatar

DOI 10.1103/PhysRevB.109.024506 · Physical Review B

T1

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Abstract

A recent theory of the disorder-dependent slope of the upper critical field at the superconducting transition temperature Tc, defined as S≡|dHc2/dT|T→Tc, is extended to multiband superconductors aimed at iron-based superconductors, considering two constant gaps of different magnitudes and, potentially, different signs. We show that the slope S decreases with increasing nonmagnetic scattering rate P in the s± pairing state and increases in the s++ superconductor for a reasonable range of parameters. The experiment shows that in a typical iron-based superconductor, Ba1−xKxFe2As2 (BaK122), the nonmagnetic disorder induced by electron irradiation leads to an increasing S(P) across the superconducting “dome,” at different x. This implies that Ba1−xKxFe2As2 is likely an s++ superconductor with two effective gaps of different magnitudes, at least at moderate doping levels, x<0.6. This work reopens a decade-long discussion about the nature of the superconducting order parameter in iron pnictides.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Ba1-xKxFe2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
MgB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
V3Si Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
YBa2Cu3O7-x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
(NdCe)2CuO4+y Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Ba(Fe1-xCox)2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
BaFe2(As1-xPx)2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
NdFeAs(O,F) Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown