ChemInform Abstract: Superconductivity at 43 K in SmFeAsO<sub>1‐x</sub>F<sub>x</sub>.

Chen, X. H.; Wu, Tong; Wu, Gang; Liu, R. H.; Chen, H H Chen; Fang, Delong

doi:10.1002/chin.200839011

Cited by 61 publications

(82 citation statements)

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“…In this paper, we report the synthesis of the new superconductor SrFe 1-x Ru x As with a T c of 13.5 K by replacing the Fe with the isoelectronic metal Ru, X-ray diffraction indicates that the material has formed the ThCr 2 Si 2 -type structure with a space group I4/mmm. The variation of the lattice parameters with Ru substitution demonstrates that the Fe ions are successfully 2 replaced by the Ru. The spin-density-wave (SDW) transition in the parent compound is suppressed with Ru doping, and superconductivity emerges.…”

Section: Introductionmentioning

confidence: 96%

“…Similar to the cuprates, the Fe-As layer is thought to be responsible for superconductivity and La-O layer is carrier reservoir layer to provide electron carrier. By replacing La with other rare earths, T c can be raised to above 50 K [2][3][4][5][6][7]. Late on, the oxygen-free iron arsenide compounds AFe 2 As 2 (denoted as FeAs-122) were discovered and superconductivity was found by appropriate substitution or under pressure [8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

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Superconductivity induced by doping Ru in SrFe2−xRuxAs2

Wang

Gao

et al. 2009

Physica C: Superconductivity

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Abstract:Using one-step solid state reaction method, we have successfully synthesized the superconductor SrFe 1-x Ru x As. X-ray diffraction indicates that the material has formed the ThCr 2 Si 2 -type structure with a space group I4/mmm. The systematic evolution of the lattice constants demonstrates that the Fe ions are successfully replaced by the Ru.By increasing the doping content of Ru, the spin-density-wave (SDW) transition in the parent compound is suppressed and superconductivity emerges. The maximum superconducting transition temperature is found at 13.5 K with the doping level of x = 0.7. The temperature dependence of DC magnetization confirms superconducting transitions at around 12 K. Our results indicate that similar to non-isoelectronic substitution, isoelectronic substitution contributes to changes in both the carrier concentration and internal pressure, and superconductivity could be induced by isoelectronic substitution.

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Superconductivity induced by doping Ru in SrFe2−xRuxAs2

Wang

Gao

et al. 2009

Physica C: Superconductivity

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“…These studies have led to the discoveries of Ce, Pr, Nd, Sm, Gd iron-based superconductors [2][3][4][5][6]. It has been established that superconductivity can be induced in this system by the substitution of fluorine for oxygen.…”

Section: Introductionmentioning

confidence: 99%

Structural and critical current properties in polycrystalline SmFeAsO_1−xF_x

Wang¹,

Gao²,

Qi³

et al. 2008

Supercond. Sci. Technol.

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A series of polycrystalline SmFeAsO 1-x F x bulks (x=0.15, 0.2, 0.3 and 0.4) were prepared by a conventional solid state reaction. Resistivity, susceptibility, magnetic hysteresis, critical current density and microstructure of these samples have been investigated. The resistivity result shows that critical transition temperature Tc increases steadily with increasing fluorine content, with the highest onset Tc=53 K at x=0.4. On the other hand, a study on the effect of lattice constants on critical transition temperature and resistivity at 60 K (ρ 60K ) presents a possible correlation; that is, Tc rises with the shrinkage of a-axis while ρ 60K increases with the enlargement of c-axis. A global critical current density of 1.1×10 4 A/cm 2 at 5 K in self field was achieved in the purest sample. An inter-grain Jc of about 3.6×10 3 A/cm 2 at 5 K in self field was estimated by comparing the difference in magnetization between powder and bulk samples, in contrast to the intra-grain Jc of 10 6 A/cm 2 . A weak field dependence was observed in the estimated inter-grain Jc, and the effect of composition gradients on the inter-grain Jc was also discussed.

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“…For the 1/T1 NMR spin relaxation rate, the inter-band contribution is consistent with the current experimental results, including a (nonuniversal) T 3 behavior and the absence of a coherence peak. However, the intra-band contribution is considerably larger than the inter-band contributions and still exhibits a small enhancement in the NMR spin relaxation rate right below Tc in the clean limit.Introduction -The recent discovery of iron-based superconductors with a transition temperature as high as 55K has stimulated a flurry of experimental and theoretical activity 2,3,4,5,6,7,8,9,10,11 . However, a conclusive observation of the pairing symmetry still remains elusive, with both nodal and nodeless order parameters reported in experimental observations.…”

mentioning

confidence: 99%

Experimental consequences of thes-wavecos(kx)cos(ky
Parish
¹
,
Hu
²
,
Bernevig
³

2008
Phys. Rev. B
116
5
106
2
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The experimental consequences of different order parameters in iron-based superconductors are theoretically analyzed. We consider both nodeless and nodal order parameters, with an emphasis on the cos(kx) · cos(ky) nodeless order parameter recently derived by two of us 1 . We analyze the effect of this order parameter on the spectral function, density of states, tunneling differential conductance, penetration depth, and the NMR spin relaxation time. This extended s-wave symmetry has line-zeroes in between the electron and hole pockets, but they do not intersect the two Fermi surfaces for moderate doping, and the superconductor is fully gapped. However, this suggests several quantitative tests: the exponential decay of the penetration depth weakens and the density of states reveals a smaller gap upon electron or hole doping. Moreover, the cos(kx) · cos(ky) superconducting gap is largest on the smallest (hole) Fermi surface. For the 1/T1 NMR spin relaxation rate, the inter-band contribution is consistent with the current experimental results, including a (nonuniversal) T 3 behavior and the absence of a coherence peak. However, the intra-band contribution is considerably larger than the inter-band contributions and still exhibits a small enhancement in the NMR spin relaxation rate right below Tc in the clean limit.Introduction -The recent discovery of iron-based superconductors with a transition temperature as high as 55K has stimulated a flurry of experimental and theoretical activity 2,3,4,5,6,7,8,9,10,11 . However, a conclusive observation of the pairing symmetry still remains elusive, with both nodal and nodeless order parameters reported in experimental observations. Numerical and analytic research suggests that the antiferromagnetic exchange coupling between Fe sites is strong 12,13,14 . Owing to As-mediated hopping, antiferromagnetic exchange exists not only between the nearest neighbor (NN) Fe sites, but also between next nearest neighbor (NNN) sites. Moreover, the NNN coupling strength J 2 is stronger than the NN coupling strength J 1 . The J 1 − J 2 model produces half-filled magnetic physics consistent with experimental neutron data 15 . A nematic magnetic phase transition has been predicted in this model 16,17 , consistent with the experimental observation of a structural transition preceding the spin density wave (SDW) formation. This model suffers, however, from an important deficiency -it is an insulator whereas the real material is an, albeit bad, metal. We, however, believe that the spin-spin interaction insight is important to the physics of the iron-pnictides.In a recent paper 1 , two of us added electron itineracy to the problem and studied a t − J 1 − J 2 model without band renormalization. We found that the singletforming J 1 − J 2 interaction gives rise to four possible pairing symmetries: cos(k x ) ± cos(k y ), sin(k x ) · sin(k y ) and cos(k x ) · cos(k y ). The last two are strongly preferred from an interaction standpoint when J 2 > J 1 , but only cos(k x ) · cos(k y ) matches the symmetry...

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ChemInform Abstract: Superconductivity at 43 K in SmFeAsO_1‐xF_x.

Cited by 61 publications

References 1 publication

Superconductivity induced by doping Ru in SrFe2−xRuxAs2

Superconductivity induced by doping Ru in SrFe2−xRuxAs2

Structural and critical current properties in polycrystalline SmFeAsO_1−xF_x

Experimental consequences of thes-wavecos(kx)cos(ky
Parish
¹
,
Hu
²
,
Bernevig
³

2008
Phys. Rev. B
116
5
106
2
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ChemInform Abstract: Superconductivity at 43 K in SmFeAsO1‐xFx.

Cited by 61 publications

References 1 publication

Superconductivity induced by doping Ru in SrFe2−xRuxAs2

Superconductivity induced by doping Ru in SrFe2−xRuxAs2

Structural and critical current properties in polycrystalline SmFeAsO1−xFx

Experimental consequences of thes-wavecos(kx)cos(kyParish1, Hu2, Bernevig3 2008Phys. Rev. B11651062View full textAdd to dashboardCite

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ChemInform Abstract: Superconductivity at 43 K in SmFeAsO_1‐xF_x.

Structural and critical current properties in polycrystalline SmFeAsO_1−xF_x

Experimental consequences of thes-wavecos(kx)cos(ky
Parish
¹
,
Hu
²
,
Bernevig
³

2008
Phys. Rev. B
116
5
106
2
View full text Add to dashboard Cite