Valence change of europium in EuFe2As1.4P0.6 and compressed EuFe2As2 and its relation to superconductivity

Liling Sun; Jing Guo; Genfu Chen; Xianhui Chen; Xiaoli Dong; Wei Lu; Chao Zhang; Zheng Jiang; Yang Zou; Suo Zhang; Yuying Huang; Qi Wu; Xi Dai; Yuanchun Li; Jing Liu; Zhongxian Zhao

doi:10.1103/PhysRevB.82.134509

Valence change of europium in EuFe2As1.4P0.6 and compressed EuFe2As2 and its relation to superconductivity

Liling Sun, Jing Guo, Genfu Chen, Xianhui Chen, Xiaoli Dong, Wei Lu, Chao Zhang, Zheng Jiang, Yang Zou, Suo Zhang, Yuying Huang, Qi Wu, Xi Dai, Yuanchun Li, Jing Liu, Zhongxian Zhao

DOI 10.1103/PhysRevB.82.134509 · Physical Review B

T1

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Abstract

Superconductivity can be realized in Eu-containing pnictides by applying chemical (internal) and physical (external) pressure, the intrinsic physical mechanism of which attracts much attention in the studies of pnictide superconductors. Here we present the experimental evidence for the pressure-induced valence change of europium in EuFe2As1.4P0.6 exposed to ambient pressure and EuFe2As2 to high pressure by x-ray absorption measurements on L3-Eu edge. We found that the absorption spectrum of EuFe2As1.4P0.6 showed a clear spectra weight transfer from divalent to trivalent state. Furthermore, a similar behavior of valence transition as in EuFe2As1.4P0.6 was also observed in EuFe2As2 when pressure was applied. This reports the observation of valence change in pnictide superconductors and the analysis of its influence on superconductivity in EuFe2As1.4P0.6 and compressed EuFe2As2.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
EuFe2As1.4P0.6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	19.4	Pressure unresolved	onset
EuFe2As1.4P0.6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	26	Pressure unresolved	unknown
EuFe2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	29.5	2.7 GPa	unknown
CaFe2As1.7P0.3 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	13	Pressure unresolved	unknown
SrFe2As1.3P0.7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	27	Pressure unresolved	unknown
BaFe2As1.4P0.6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	30	Pressure unresolved	unknown
CaFe2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	11	0.5 GPa	unknown
SrFe2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	28	3.25 GPa	unknown
BaFe2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	29	4 GPa	unknown
EuFe1.715Co0.285As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	24	Pressure unresolved	unknown