Investigation of the superconducting gap structure in SrFe2(As0.7P0.3)2 by magnetic penetration depth and flux flow resistivity analysis

Abstract

We measured the microwave surface impedances and obtained the superfluid density and flux flow resistivity in single crystals of a phosphor-doped iron-based superconductor SrFe2(As1−xPx)2 single crystals (x=0.30, Tc=25K). At low temperatures, the superfluid density, ns(T)/ns(0), obeys a power law, ns(T)/ns(0)=1−C(T/Tc)n, with a fractional exponent of n=1.5–1.6. The flux flow resistivity was significantly enhanced at low magnetic fields. These features are consistent with the presence of line nodes on at least one band and modulated nodeless gap with deep minimum on the same bands and/or other bands. The remarkable difference observed in the superconducting gap structure between SrFe2(As1−xPx)2 and BaFe2(As1−xPx)2 in our experiments is important for clarifying the mechanism of iron-based superconductivity in the 122 system.

Source-reported materials — not catalogue approval

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