Evolution of correlation strength in KxFe2–ySe2 superconductor doped with S

Kefeng Wang (王克锋); Hechang Lei (雷和畅); C. Petrovic

doi:10.1103/PhysRevB.84.054526

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Evolution of correlation strength in KxFe2–ySe2 superconductor doped with S

Kefeng Wang (王克锋), Hechang Lei (雷和畅), C. Petrovic

DOI 10.1103/PhysRevB.84.054526 · Physical Review B

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Abstract

We report the evolution of thermal transport properties of KxFe2–ySe2 with sulfur substitution at Se sites. Sulfur doping suppresses the superconducting Tc. The Seebeck coefficient of all crystals in the low-temperature range can be described very well by a diffusive thermoelectric response model. The zero-temperature extrapolated value of the Seebeck coefficient divided by temperature, S/T, gradually decreases from −0.48 μV/K2 to a very small value, ∼0.03 μV/K2, where Tc is completely suppressed. The normal-state electron Sommerfeld term (γn) of specific heat also decreases with the increase in sulfur content. The decrease of S/T and γn reflects a suppression of the density of states at the Fermi energy, or a change in the Fermi surface that would induce the suppression of correlation strength. Our results imply little relevance of strong electron correlations to superconductivity.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
LaFeAsO Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	26	Pressure not reported	unknown
K0.64Fe1.44Se2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	31	Pressure not reported	unknown
K0.73Fe1.44Se1.68S0.32 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	31.4	Pressure not reported	unknown
K0.70Fe1.55Se1.01S0.99 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	21.4	Pressure not reported	unknown
K0.76Fe1.61Se0.96S1.04 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	16.4	Pressure not reported	unknown