Superconductivity and phase diagram in iron-based arsenic-oxides ReFeAsO
                    <sub>1−δ</sub>
                    (Re = rare-earth metal) without fluorine doping

Ren, Zhi-An; Che, G.C.; Dong, Xianlin; Yang, Jie; Lü, Wei; Yi, Wei; Shen, Xiaoli; Li, Zhengcai; Sun, Liling; Zhou, Fang; Zhao, Zhongxian

doi:10.1209/0295-5075/83/17002

Cited by 689 publications

(423 citation statements)

References 16 publications

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“…The single crystalline nature of the samples was checked by Laue X-ray diffraction [38]. Our crystals, whose T c (≈ 35 K) is lower than the optimum T c ≈ 51 K of PrFeAsO 1−y [39], are in the underdoped regime (y ∼ 0.1) [40], which is close to the spin-density-wave order [41]. The sample homogeneity was checked by magneto-optical (MO) imaging [37].…”

Section: Experimental a Single Crystalsmentioning

confidence: 98%

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Shibauchi

Hashimoto

Okazaki

et al. 2009

Physica C: Superconductivity

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In this article, we review our recent studies of microwave penetration depth, lower critical fields, and quasiparticle conductivity in the superconducting state of Fe-arsenide superconductors. Highsensitivity microwave surface impedance measurements of the in-plane penetration depth λ ab in single crystals of electron-doped PrFeAsO1−y (y ∼ 0.1) and hole-doped Ba1−xKxFe2As2 (x ≈ 0.55) are presented. In clean crystals of Ba1−xKxFe2As2, as well as in PrFeAsO1−y crystals, the penetration depth shows flat temperature dependence at low temperatures, indicating that the superconducting gap opens all over the Fermi surface. The temperature dependence of superfluid density λ 2 ab (0)/λ 2 ab (T ) in both systems is most consistent with the existence of two different gaps. In Ba1−xKxFe2As2, we find that the superfluid density is sensitive to degrees of disorder inherent in the crystals, implying unconventional impurity effect. We also determine the lower critical field Hc1 in PrFeAsO1−y by using an array of micro-Hall probes. The temperature dependence of Hc1 saturates at low temperatures, fully consistent with the superfluid density determined by microwave measurements. The anisotropy of Hc1 has a weak temperature dependence with smaller values than the anisotropy of upper critical fields at low temperatures, which further supports the multi-gap superconductivity in Fe-arsenide systems. The quasiparticle conductivity shows an enhancement in the superconducting state, which suggests the reduction of quasiparticle scattering rate due to the gap formation below Tc. From these results, we discuss the structure of the superconducting gap in these Fe-arsenides, in comparison with the high-Tc cuprate superconductors.

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Section: Experimental a Single Crystalsmentioning

confidence: 98%

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Shibauchi

Hashimoto

Okazaki

et al. 2009

Physica C: Superconductivity

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“…[9] Superconducting 1111-materials have also been produced by the introduction of O-vacancies. [10] Here we describe the results of isoelectronic substitution of Ru for Fe in PrFeAsO 1111-type materials which fully suppresses the SDW transition resulting in a metallic state that does not exhibit superconductivity above 2 K.…”

Section: Introductionmentioning

confidence: 99%

“…[13] Superconductivity has been observed with transition temperatures (T C ) as high as 52 K in PrFeAsO 1−x F x and 51 K in PrFeAsO 1−y . [14,10] It has been shown that the superconductivity in these systems is quite robust against disorder, even disorder in the Fe plane. [6,15] It is possible that disorder alone, without charge carrier doping, may be enough to suppress the SDW so that superconductivity could emerge.…”

Section: Introductionmentioning

confidence: 99%

Suppression of spin density wave by isoelectronic substitution in

McGuire

Singh

Sefat

et al. 2009

Journal of Solid State Chemistry

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We have studied the effects of the isoelectronic substitution of Ru for Fe in polycrystalline samples of the spin density wave (SDW) material PrFeAsO. Crystal structures from powder x-ray diffraction at room temperature and transport properties from 2−300 K are reported. The SDW is completely suppressed upon Ru substitution. The distortion of the tetrahedral coordination environment of the transition metal site increases as the Ru concentration increases, which may be related to the absence of superconductivity above 2 K. Band structure calculations show that the larger size of Ru 4d orbitals is primarily responsible for the suppression of magnetism as Ru is substituted into the Fe layer. The experimental results indicate that long-ranged magnetic order of Pr moments is suppressed at Ru concentrations as low as 10%.

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“…An example is the maximum T c of approximately 56 K achieved by the substitution of rare-earth ions in the 1111 system. 29 It is thus somewhat surprising that substitution of K by Rb, Cs, or Tl in the new superconductors leaves T c essentially unaltered at around 30 K. 28 This result poses another fundamental question, concerning why superconductivity should be so robust in the AFeSe system, and its answer requires a careful investigation into the effect of Tl, Rb, and Cs substitution on the microstructure of the FeSe layers in these materials.…”

mentioning

confidence: 99%

Effect of iron content and potassium substitution inA0.8Fe1.6Se2
Zhang
¹
,
Liu
²
,
He
³

et al. 2012
Phys. Rev. B
17
4
12
0
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We have performed Raman-scattering measurements on high-quality single crystals of the superconductors K0.8Fe1.6Se2 (Tc = 32 K), Tl0.5K0.3Fe1.6Se2 (Tc = 29 K), and Tl0.5Rb0.3Fe1.6Se2 (Tc = 31 K), as well as of the insulating compound KFe1.5Se2. To interpret our results, we have made first-principles calculations for the phonon modes in the ordered iron-vacancy structure of K0.8Fe1.6Se2. The modes we observe can be assigned very well from our symmetry analysis and calculations, allowing us to compare Raman-active phonons in the AFeSe compounds. We find a clear frequency difference in most phonon modes between the superconducting and non-superconducting potassium crystals, indicating the fundamental influence of iron content. By contrast, substitution of K by Tl or Rb in A0.8Fe1.6Se2 causes no substantial frequency shift for any modes above 60 cm −1 , demonstrating that the alkali-type metal has little effect on the microstructure of the FeSe layer. Several additional modes appear below 60 cm −1 in Tl-and Rb-substituted samples, which are vibrations of heavier Tl and Rb ions. Finally, our calculations reveal the presence of "chiral" phonon modes, whose origin lies in the chiral nature of the K0.8Fe1.6Se2 structure.

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Superconductivity and phase diagram in iron-based arsenic-oxides ReFeAsO _1−δ (Re = rare-earth metal) without fluorine doping

Cited by 689 publications

References 16 publications

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Suppression of spin density wave by isoelectronic substitution in

Effect of iron content and potassium substitution inA0.8Fe1.6Se2
Zhang
¹
,
Liu
²
,
He
³

et al. 2012
Phys. Rev. B
17
4
12
0
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Superconductivity and phase diagram in iron-based arsenic-oxides ReFeAsO 1−δ (Re = rare-earth metal) without fluorine doping

Cited by 689 publications

References 16 publications

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors

Suppression of spin density wave by isoelectronic substitution in

Effect of iron content and potassium substitution inA0.8Fe1.6Se2Zhang1, Liu2, He3 et al. 2012Phys. Rev. B174120View full textAdd to dashboardCite

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Superconductivity and phase diagram in iron-based arsenic-oxides ReFeAsO _1−δ (Re = rare-earth metal) without fluorine doping

Effect of iron content and potassium substitution inA0.8Fe1.6Se2
Zhang
¹
,
Liu
²
,
He
³

et al. 2012
Phys. Rev. B
17
4
12
0
View full text Add to dashboard Cite