1207.1185 (H. Mukuda et al.)

High-Tc Nodeless s_\pm-wave Superconductivity in Y(La)FeAsO_{1-y} with
Tc=50 K: 75As-NMR Study    [PDF]

H. Mukuda, S. Furukawa, H. Kinouchi, M. Yashima, Y. Kitaoka, P. M. Shirage, H. Eisaki, A. Iyo

We report 75As-NMR study on the Fe-pnictide high-Tc superconductor Y0.95La0.05FeAsO_{1-y} (Y0.95La0.051111) with Tc=50 K that includes no magnetic rare-earth elements. The measurement of the nuclear-spin lattice-relaxation rate 75(1/T1) has revealed that the nodeless bulk superconductivity takes place at Tc=50 K while antiferromagnetic spin fluctuations (AFSFs) develop moderately in the normal state. These features are consistently described by the multiple fully-gapped s_\pm-wave model based on the Fermi-surface (FS) nesting. Incorporating the theory based on band calculations, we propose that the reason that Tc=50 K in Y0.95La0.051111 is larger than Tc=28 K in La1111 is that the FS multiplicity is maximized, and hence the FS nesting condition is better than that in La1111.

View original: http://arxiv.org/abs/1207.1185