Superconducting phases in (NH3)yMxFeSe1−zTez (M=Li,Na,andCa)

Yusuke Sakai; Lu Zheng; Masanari Izumi; Kazuya Teranishi; Ritsuko Eguchi; Hidenori Goto; Taiki Onji; Shingo Araki; Tatsuo C. Kobayashi; Yoshihiro Kubozono

doi:10.1103/PhysRevB.89.144509

Superconducting phases in (NH3)yMxFeSe1−zTez (M=Li,Na,andCa)

Yusuke Sakai, Lu Zheng, Masanari Izumi, Kazuya Teranishi, Ritsuko Eguchi, Hidenori Goto, Taiki Onji, Shingo Araki, Tatsuo C. Kobayashi, Yoshihiro Kubozono

DOI 10.1103/PhysRevB.89.144509 · Physical Review B

T1

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Abstract

Superconducting phases of (NH3)yMxFeSe1−zTez have been synthesized by the intercalation of metal atoms (M:Li,Na,Ca) into FeSe and FeSe0.5Te0.5 using a low-temperature liquid NH3 technique. The superconducting transition temperature (Tc) is 31.5 K for Na-doped FeSe, and for Li-, Na-, and Ca-doped FeSe0.5Te0.5 it is 26, 22, and 17 K, respectively. The 31.5 K superconducting is the superconducting phase in ammoniated Na-doped FeSe. The Tc is lower than that (onset Tc=46K) of the superconducting phase reported previously. The reason why the Tc of this phase is lower is discussed based on the structure. The pressure dependences of Tc in the (NH3)yNa0.5FeSe and (NH3)yNa0.4FeSe0.5Te0.5 samples have been measured and a negative pressure dependence is observed; i.e., a decrease in lattice constant c leads to a decrease in Tc, consistent with the behavior of (NH3)yCs0.4FeSe reported previously by our group. Furthermore, the magnetic behavior of (NH3)yNa0.4FeSe0.5Te0.5 has been fully investigated at different applied magnetic fields (H) to determine the critical magnetic field. This is a successful metal intercalation into FeSe1−zTez (z≠0) and an observation of superconductivity.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
(NH3)yNa0.5FeSe Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	31.5	Pressure unresolved	midpoint
(NH3)yNa0.5FeSe Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	36	Pressure unresolved	onset
(NH3)yLi0.5FeSe0.5Te0.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	26	Pressure not reported	unknown
(NH3)yNa0.4FeSe0.5Te0.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	22	Pressure unresolved	midpoint
(NH3)yNa0.4FeSe0.5Te0.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	24	Pressure unresolved	onset
(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
FeSe0.5Te0.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	14.2	Pressure unresolved	onset
FeSe Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	9	Pressure unresolved	onset
(NH3)yNa0.5FeSe Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	46	Pressure not reported	onset
(NH3)yCs0.4FeSe Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	33.6	Pressure not reported	unknown