Superconducting Energy Gap and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>c</mml:mi></mml:math>-Axis Plasma Frequency of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo stretchy="false">(</mml:mo><mml:mi>Nd</mml:mi><mml:mo>,</mml:mo><mml:mi>Sm</mml:mi><mml:mo stretchy="false">)</mml:mo><mml:msub><mml:mi>FeAsO</mml:mi><mml:mn>0.82</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">F</mml:mi><mml:mn>0.18</mml:mn></mml:msub></mml:ma

Dubroka, Adam; Kim, Kyung Wan; Rössle, Matthias; Malik, V. K.; Drew, Alan J.; Liu, R. H.; Wu, Gang; Chen, X. H.; Bernhard, C.

doi:10.1103/physrevlett.101.097011

Cited by 58 publications

(63 citation statements)

References 29 publications

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“…To further minimize the influence of pinning, we partly applied a vortex-lattice shaking technique [25]. With this technique the relaxation of the vortex-lattice towards its thermal equilibrium is strongly enhanced by using an additional [8,11,12,13,14]. At low temperatures pinning effects give rise to the rather large errors in the anisotropy parameter, preventing a reliable determination of γ for T < 19 K. In order to demonstrate that the strong temperature dependence of γ is not an artefact of the increasing pinning strength at low temperatures, we compared shaked and unshaked torque data.…”

Section: Methodsmentioning

confidence: 99%

“…According to theoretical predictions superconductivity takes place in the FeAs layers, whereas the LaO layers are charge reservoirs when doped with F ions [8,9]. An estimation of γ ≥ 30 at T = 0 K was made for SmFeAsO 0.82 F 0.18 from measurements of the c-axis plasma frequency using infrared ellipsometry [11]. From point-contact spectroscopy [12] and resistivity experiments [13] on LaFeAsO 0.9 F 0.1−δ the anisotropy parameter was estimated to be γ ≃ 10.…”

Section: Introductionmentioning

confidence: 99%

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Anisotropy of Superconducting Single Crystal SmFeAsO0.8F0.2 Studied by Torque Magnetometry

Weyeneth

Puźniak

Mosele

et al. 2008

J Supercond Nov Magn

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Single crystals of the oxypnictide superconductor SmFeAsO 0.8 F 0.2 with T c ≃ 45(1) K were investigated by torque magnetometry. The crystals of mass ≤ 0.1 µg were grown by a high-pressure cubic anvil technique. The use of a high-sensitive piezoresistive torque sensor made it possible to study the anisotropic magnetic properties of these tiny crystals. The anisotropy parameter γ was found to be field independent, but varies strongly with temperature ranging from γ ≃ 8 at T T c to γ ≃ 23 at T ≃ 0.4T c . This unusual behavior of γ signals unconventional superconductivity.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Anisotropy of Superconducting Single Crystal SmFeAsO0.8F0.2 Studied by Torque Magnetometry

Weyeneth

Puźniak

Mosele

et al. 2008

J Supercond Nov Magn

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“…And although much has been made recently of the differences these materials have from the cuprates, other studies show some similarities. Various photoemission [43], tunneling [44], and optics [45] studies are quite reminiscent of the cuprates, including the possible presence of a precursor gap (a "pseudogap") existing above T c . Pursuing the various similarities and differences between these two classes of materials may help unravel the physics of both of them.…”

Section: Subject Areas: Superconductivitymentioning

confidence: 99%

High-temperature superconductivity in the iron pnictides

Norman

2008

Physics

183

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“…3c the gap-like suppression of the infrared optical conductivity, σ 1 , is a clear signature of bulk superconductivity. This suppression is less pronounced at x = 0.13, but this may be understood due to the lower onset frequency and thus gap magnitude 21 (as marked by the arrows) and the reduced condensate density 22,23 . Our infrared data thus are hardly compatible with the point of view that the superconducting volume fraction is more than an order of magnitude smaller at x = 0.13 than at x = 0.15 and 0.18 where a nearly 100% superconducting volume fraction is established from μSR (ref.…”

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confidence: 99%

Coexistence of static magnetism and superconductivity in SmFeAsO1−xFx as revealed by muon spin rotation

et al. 2009

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The recent observation of superconductivity with critical temperatures (T c ) up to 55 K in the pnictide RFeAsO 1−x F x , where R is a lanthanide, marks the first discovery of a noncopper-oxide-based layered high-T c superconductor 1-3 . It has raised the suspicion that these new materials share a similar pairing mechanism to the cuprate superconductors, as both families exhibit superconductivity following charge doping of a magnetic parent material. In this context, it is important to follow the evolution of the microscopic magnetic properties of the pnictides with doping and hence to determine whether magnetic correlations coexist with superconductivity. Here, we present a muon spin rotation study on SmFeAsO 1−x F x , with x = 0-0.30 that shows that, as in the cuprates, static magnetism persists well into the superconducting regime. This analogy is quite surprising as the parent compounds of the two families have rather different magnetic ground states: itinerant spin density wave for the pnictides contrasted with the MottHubbard insulator in the cuprates. Our findings therefore suggest that the proximity to magnetic order and associated soft magnetic fluctuations, rather than strong electronic correlations in the vicinity of a Mott-Hubbard transition, may be the key ingredients of high-T c superconductors.Similar to the cuprates, the pnictide high-critical-temperature (T c ) superconductors (HTSCs) have a layered structure comprising alternating FeAs and LaO sheets, with the Fe arranged on a square lattice 1 . Theoretical calculations predict a quasi-twodimensional electronic structure, with LaO layers that mainly act as blocking layers and metallic FeAs layers that are responsible for superconductivity [4][5][6] , although these are multiband superconductors with up to five FeAs-related bands crossing the Fermi level [4][5][6][7] . Like the copper-oxide HTSCs, the superconducting state in the pnictides emerges on charge doping a magnetic parent compound [8][9][10] , with indications that the maximal T c occurs just as magnetism disappears [11][12][13] . The last point may well be of great significance, as the parent compounds in the two families are very different. For the pnictides, there are strong indications that they are itinerant systems with magnetism arising from a nesting-induced spin density wave (SDW). This is in contrast to the cuprates, where it is well established that the mother compounds are 'charge transfer insulators', where strongly repulsive electronic correlations yield an insulating and antiferromagnetic ground state despite a half-filled conduction band. It is therefore of great importance to obtain further insight into the differences and similarities of the pnictide and cuprate HTSCs. A particularly important question is how magnetism and superconductivity evolve on electron doping. In this context, muon spin rotation (μSR) is an ideal technique as it provides microscopic information corresponding to the bulk of a sample and there is a substantial body of μSR data that has been colle...

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Superconducting Energy Gap andc-Axis Plasma Frequency of(Nd,Sm)FeAsO0.82F0.18

Cited by 58 publications

References 29 publications

Anisotropy of Superconducting Single Crystal SmFeAsO0.8F0.2 Studied by Torque Magnetometry

Anisotropy of Superconducting Single Crystal SmFeAsO0.8F0.2 Studied by Torque Magnetometry

High-temperature superconductivity in the iron pnictides

Coexistence of static magnetism and superconductivity in SmFeAsO1−xFx as revealed by muon spin rotation

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