Superconductivity at 57.3 K in La-Doped Iron-Based Layered Compound Sm0.95La0.05O0.85F0.15FeAs

Wei, Zhiguo; Li, Hai’ou; Hong, Wei-Li; Lv, Zheng; Wu, Huiyan; Guo, Xing; Ruan, Keqing

doi:10.1007/s10948-008-0327-y

Cited by 39 publications

(24 citation statements)

References 3 publications

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“…They consist of the similar FeSe-layers to carry the majority of the conducting carriers. However, the maximum T c s obtained for different classes of both families are 57 K for 1111 (10,11); 38 K for 122 (3,4,12); 18-31 K for 111 (5, 6); and 8-37 K for 11 (8,9), through doping and/or pressurization. In spite of the similar layered structures, T c s of Fe-pnictides and -chalcogenides are much lower than those of the cuprates, which possess the CuO 2 -layers (13).…”

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confidence: 93%

Unusual superconducting state at 49 K in electron-doped CaFe ₂ As ₂ at ambient pressure

Deng

Gooch

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

127

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We report the detection of unusual superconductivity up to 49 K in single crystalline CaFe 2 As 2 via electron-doping by partial replacement of Ca by rare-earth. The superconducting transition observed suggests the possible existence of two phases: one starting at 49 K, which has a low critical field < 4 Oe, and the other at 21 K, with a much higher critical field > 5 T. Our observations are in strong contrast to previous reports of doping or pressurizing layered compounds AeFe 2 As 2 (or Ae122), where Ae = Ca, Sr, or Ba. In Ae122, hole-doping has been previously observed to generate superconductivity with a transition temperature ( T c ) only up to 38 K and pressurization has been reported to produce superconductivity with a T c up to 30 K. The unusual 49 K phase detected will be discussed.

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confidence: 93%

Unusual superconducting state at 49 K in electron-doped CaFe ₂ As ₂ at ambient pressure

Deng

Gooch

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

127

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“…The Fe-based layered pnictides and chalcogenides upon doping or under pressure constitute an interesting superconductor class with a transition temperature T c as high as 57 K [1] , second only to that of ≤ 134 K at ambient [2] or 164 K under pressure [3] of the layered cuprate class. These superconductors comprise four families with their respective maximum T c s at ambient as: 1111 (RFeAsO)-57 K [1]; 122 (AEFe 2 As 2 or AE122)-38 K [4,5] ; 111 (AFeAs)-18 K [6]; and 11 (FeSe)-10 K [7], where R = rare-earth, AE = alkaline earth, and A = alkaline, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…These superconductors comprise four families with their respective maximum T c s at ambient as: 1111 (RFeAsO)-57 K [1]; 122 (AEFe 2 As 2 or AE122)-38 K [4,5] ; 111 (AFeAs)-18 K [6]; and 11 (FeSe)-10 K [7], where R = rare-earth, AE = alkaline earth, and A = alkaline, respectively. While doping by K or Na in the AE-sites generates bulk superconductivity with a maximum T c ~ 33-38 K as evidenced calorimetrically in all AE122 [8], pressure induces superconductivity with a similar maximum T c only in Ba122 and Sr122 [9].…”

Section: Introductionmentioning

confidence: 99%

Evidence for defect-induced superconductivity up to 49 K in(Ca1−xRx)Fe2

Deng

Zhao

et al. 2016

Phys. Rev. B

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To explore the origin of the unusual non-bulk superconductivity with a T c up to 49 K reported in the rareearth-doped CaFe 2 As 2 , the chemical composition, magnetization, specific heat, resistivity, and annealing effect are systematically investigated on nominal (Ca 1-x R x )Fe 2 As 2 single crystals with different x's and R = La, Ce, Pr, and Nd. All display a doping-independent T c once superconductivity is induced, a doping-dependent low field superconducting volume fraction f, and a large magnetic anisotropy η in the superconducting state, suggesting a rather inhomogeneous superconducting state in an otherwise microscale-homogenous superconductor. The wavelength dispersive spectroscopy and specific heat show the presence of defects which are closely related to f, regardless of the R involved. The magnetism further reveals that the defects are mainly superparamagnetic clusters for R = Ce, Pr, and Nd with strong intercluster interactions, implying that defects are locally self-organized. Annealing at 500 °C, without varying the doping level x, suppresses f profoundly but not the T c . The above observations provide evidence for the crucial role of defects in the occurrence of the unusually high T c ~ 49 K in (Ca 1-x R x )Fe 2 As 2 and are consistent with the interface-enhanced superconductivity recently proposed.

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“…For a long time after the discovery of 122-type superconductors, hole-doped compounds Ba 1−x KxFe 2 As 2 (x~0.4) possess the highest Tc around 38 K [2], lower than the maximum Tc value (~57 K) in 1111 system [11]. In the end of 2011, Sara et al [12] reported that superconductivity with Tc as high as 47 K could be induced by rare earth element doping in the 122 parent compound CaFe 2 As 2 .…”

Section: Introductionmentioning

confidence: 99%

Review on origin of the unusual high-Tc superconductivity in Ca1−xRExFe2As2 (RE = La, Ce, Pr, Nd)

Zhou¹,

Shi²

2015

Novel Superconducting Materials

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Review on origin of the unusual high-T c superconductivity in Ca 1−x RE x Fe 2 As 2 (RE = La, Ce, Pr, Nd) Abstract: Since the discovery of high temperature superconductivity in iron pnictides in 2008, many iron-based superconductors (IBSs) with various crystal structures have been exploited. Among them, superconductivity with the onset transition temperature Tc up to 49 K has been detected in rare earth element doped CaFe 2 As 2 system (CaRE122). The electron doping induced high Tc values clearly exceed the highest Tcs induced by both hole doping (~38 K) and chemical or physical pressure (~33 K) in the 122-type iron-based superconductors. The occurrence of high-Tc superconductivity in this unique system is quite strange in terms of the much lower Tc observed in the sister compounds bearing structural and chemical similarities. Though the high-Tc superconductivity in Ca 1−x RExFe 2 As 2 is of the non-bulk feature, its superconducting origin served as a most important question has attracted tremendous attentions ever since its discovery. In this review, we summarize the previous experimental results observed in this series of superconductors and list the possible key points that may be related to the understanding of the nature for the strange high-Tc superconductivity.

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Superconductivity at 57.3 K in La-Doped Iron-Based Layered Compound Sm0.95La0.05O0.85F0.15FeAs

Cited by 39 publications

References 3 publications

Unusual superconducting state at 49 K in electron-doped CaFe ₂ As ₂ at ambient pressure

Unusual superconducting state at 49 K in electron-doped CaFe ₂ As ₂ at ambient pressure

Evidence for defect-induced superconductivity up to 49 K in(Ca1−xRx)Fe2

Review on origin of the unusual high-Tc superconductivity in Ca1−xRExFe2As2 (RE = La, Ce, Pr, Nd)

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Superconductivity at 57.3 K in La-Doped Iron-Based Layered Compound Sm0.95La0.05O0.85F0.15FeAs

Cited by 39 publications

References 3 publications

Unusual superconducting state at 49 K in electron-doped CaFe 2 As 2 at ambient pressure

Unusual superconducting state at 49 K in electron-doped CaFe 2 As 2 at ambient pressure

Evidence for defect-induced superconductivity up to 49 K in(Ca1−xRx)Fe2

Review on origin of the unusual high-Tc superconductivity in Ca1−xRExFe2As2 (RE = La, Ce, Pr, Nd)

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Unusual superconducting state at 49 K in electron-doped CaFe ₂ As ₂ at ambient pressure

Unusual superconducting state at 49 K in electron-doped CaFe ₂ As ₂ at ambient pressure