Antiferromagnetic Spin Fluctuations above the Dome-Shaped and Full-Gap Superconducting States of LaFeAsO1−xFx Revealed by As75-Nuclear Quadrupole Resonance
T. Oka, Z. Li, S. Kawasaki, G. F. Chen, N. L. Wang, Guo-qing Zheng
DOI 10.1103/PhysRevLett.108.047001 · Physical Review Letters
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Abstract
We report a systematic study by As75 nuclear-quadrupole resonance in LaFeAsO1−xFx. The antiferromagnetic spin fluctuation found above the magnetic ordering temperature TN=58 K for x=0.03 persists in the regime 0.04≤x≤0.08, where superconductivity sets in. A dome-shaped x dependence of the superconducting transition temperature Tc is found, with the highest Tc=27 K at x=0.06, which is realized under significant antiferromagnetic spin fluctuation. With increasing x further, the antiferromagnetic spin fluctuation decreases, and so does Tc. These features resemble closely the cuprates La2−xSrxCuO4. In x=0.06, the spin-lattice relaxation rate (1/T1) below Tc decreases exponentially down to 0.13Tc, which unambiguously indicates that the energy gaps are fully opened. The temperature variation of 1/T1 below Tc is rendered nonexponential for other x by impurity scattering.
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 not reported | unknown |
| LaFeAsO0.96F0.04 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 21 | Pressure not reported | unknown |
| LaFeAsO0.94F0.06 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 27 | Pressure not reported | unknown |
| 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 | unknown |
| LaFeAsO0.90F0.10 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 18 | Pressure not reported | unknown |
| LaFeAsO0.85F0.15 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 12 | Pressure not reported | unknown |
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