Enhancement of the critical temperature of the pnictide superconductor LaFeAsO1−xFx studied via A75s NMR under pressure
Tatsuya Nakano, Naoki Fujiwara, Kenichiro Tatsumi, Hironari Okada, Hiroki Takahashi, Yoichi Kamihara, Masahiro Hirano, Hideo Hosono
DOI 10.1103/PhysRevB.81.100510 · Physical Review B
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Abstract
Nuclear-magnetic-resonance measurements of an iron (Fe)-based superconductor LaFeAsO1−xFx (x=0.08 and 0.14) were performed at ambient pressure and under pressure. The relaxation rate 1/T1 for the overdoped samples (x=0.14) shows T-linear behavior just above Tc, and pressure application enhances 1/T1T similar to the behavior of Tc. This implies that 1/T1T=constant originates from the Korringa relation, and an increase in the density of states at the Fermi energy D(EF) leads to the enhancement of Tc. In the underdoped samples (x=0.08), 1/T1 measured at ambient pressure also shows T-linear behavior in a wide temperature range above Tc. However, 1/T1T shows Curie-Weiss-type T dependence at 3.0 GPa accompanied by a small increase in Tc, suggesting that predominant low-frequency antiferromagnetic fluctuation is not important for development of superconductivity or remarkable enhancement of Tc. The qualitatively different features between underdoped and overdoped samples are systematically explained by a band calculation with hole and electron pockets.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| LaFeAsO1-xFx Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 26 | Pressure unresolved | onset |
| LaFeAsO1-xFx Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 20 | Pressure unresolved | onset |
| LaFeAsO1-xFx Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 43 | 4 GPa | onset |
| LaFeAsO1-xFx Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 43 | 4 GPa | onset |
| LaFeAsO0.92F0.08 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure unresolved | onset |
| LaFeAsO0.86F0.14 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure unresolved | onset |
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