Two superconducting gaps in LaFeAsO0.92F0.08 revealed by A75s nuclear quadrupole resonance
S. Kawasaki, K. Shimada, G. F. Chen, J. L. Luo, N. L. Wang, Guo-qing Zheng
DOI 10.1103/PhysRevB.78.220506 · Physical Review B
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Abstract
We report A75s nuclear quadrupole resonance studies on superconducting oxypnictide LaFeAsO0.92F0.08 (Tc=23 K). The temperature dependence of the spin-lattice relaxation rate (1/T1) decreases below Tc without a coherence (Hebel-Slichter) peak and shows a temperature dependence that is not simple power law nor exponential. We show that the result can be understood in terms of two superconducting gaps of either d- or ±s-wave symmetry, with the larger gap Δ1∼4kBTc and the smaller one Δ2∼1.5kBTc. Our result suggests that the multiple-gap feature is universal in the oxypnictide superconductors, which is probably associated with the multiple electronic band structures in this class of materials. We also find that 1/T1T above Tc increases with decreasing temperature, which suggests weak magnetic fluctuations in the normal state.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| LaFeAsO0.92F0.08 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 23 | Pressure unresolved | onset |
| LaFeAsO0.92F0.08 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 23 | Pressure not reported | onset |
| LaFeAsO1-xFx Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 26 | Pressure not reported | unknown |
| PrFeAsO0.89F0.11 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 45 | Pressure not reported | unknown |
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