Superconductivity in (NH3)yNaxFeSe0.5Te0.5

Lu Zheng; Yusuke Sakai; Xiao Miao; Saki Nishiyama; Takahiro Terao; Ritsuko Eguchi; Hidenori Goto; Yoshihiro Kubozono

doi:10.1103/PhysRevB.94.174505

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Superconductivity in (NH3)yNaxFeSe0.5Te0.5

Lu Zheng, Yusuke Sakai, Xiao Miao, Saki Nishiyama, Takahiro Terao, Ritsuko Eguchi, Hidenori Goto, Yoshihiro Kubozono

DOI 10.1103/PhysRevB.94.174505 · Physical Review B

T1

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Abstract

Na-intercalated FeSe0.5Te0.5 was prepared using the liquid NH3 technique, and a superconducting phase exhibiting a superconducting transition temperature (Tc) as high as 27 K was discovered. This can be called the high-Tc phase since a 21 K superconducting phase was previously obtained in (NH3)yNaxFeSe0.5Te0.5. The chemical composition of the high-Tc phase was determined to be (NH3)0.61(4)Na0.63(5)Fe0.85Se0.55(3)Te0.44(2). The x-ray diffraction patterns of both phases show that a larger lattice constant c (i.e., FeSe0.5Te0.5 plane spacing) produces a higher Tc. This behavior is the same as that of metal-doped FeSe, suggesting that improved Fermi-surface nesting produces the higher Tc. The high-Tc phase converted to the low-Tc phase within several days, indicating that it is a metastable phase. The temperature dependence of resistance for both phases was recorded at different magnetic fields, and the critical fields were determined for both phases. Finally, the Tc versus c phase diagram was prepared for the metal-doped FeSe0.5Te0.5, which is similar to that of metal-doped FeSe, although the Tc is lower.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
(NH3)yNaxFeSe0.5Te0.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	27	Pressure not reported	unknown
(NH3)yNaxFeSe0.5Te0.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	21	Pressure not reported	unknown
(NH3)0.61Na0.63Fe0.85Se0.55Te0.44 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	27	Pressure not reported	unknown
(NH3)yCa0.4FeSe0.5Te0.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	17	Pressure not reported	unknown
(NH3)yNa0.4FeSe0.5Te0.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	21	Pressure not reported	unknown
(NH3)yLi0.4FeSe0.5Te0.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	26	Pressure not reported	unknown
FeSe Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8	Pressure not reported	unknown
FeSe0.5Te0.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	14	Pressure not reported	unknown
(NH3)yNa0.4FeSe0.5Te0.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	27	Pressure not reported	unknown
(NH3)yNa0.6FeSe0.5Te0.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	30	Pressure not reported	unknown
(NH3)0.03Na0.7Fe1.33Se0.48Te0.52 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	21.5	Pressure not reported	unknown
(NH3)yNa0.5FeSe0.5Te0.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	27	Pressure not reported	unknown