Superconducting Energy Gap and c-Axis Plasma Frequency of (Nd,Sm)FeAsO0.82F0.18 Superconductors from Infrared Ellipsometry
A. Dubroka, K. W. Kim, M. Rössle, V. K. Malik, A. J. Drew, R. H. Liu, G. Wu, X. H. Chen, C. Bernhard
DOI 10.1103/PhysRevLett.101.097011 · Physical Review Letters
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Abstract
We present far-infrared ellipsometric measurements of polycrystalline samples of the pnictide superconductor RFeAsO0.82F0.18 (R=Nd and Sm). We find evidence that the electronic properties are strongly anisotropic such that the optical spectra are dominated by the weakly conducting c-axis response similar to the cuprate high-temperature superconductors. We deduce an upper limit of the c-axis superconducting plasma frequency of ωpl,cSC≤260 cm−1 corresponding to a lower limit of the c-axis magnetic penetration depth of λc≥6 μm and λc/λab≥30 as compared to λab=185 nm from muon spin rotation [A. Drew et al., arXiv:0805.1042 [Phys. Rev. Lett. (to be published)]]. We also observe a gaplike suppression of the conductivity in the superconducting state with a shoulderlike feature at ωSC*≈300 cm−1 and spectral shape which is consistent with an unconventional order parameter with 2Δ≈ωSC*≈37 meV.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| NdFeAsO0.82F0.18 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 52 | Pressure not reported | midpoint |
| NdFeAsO0.82F0.18 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 52 | Pressure not reported | midpoint |
| SmFeAsO0.82F0.18 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 45 | Pressure not reported | midpoint |
| SmFeAsO0.82F0.18 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 45 | Pressure not reported | midpoint |
| LaO0.9F0.1FeAs Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
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