title: High-Tc nodeless s±-wave superconductivity in (Y,La)FeAsO(1-y) with Tc=50 K:75As-NMR study.
abstract: We report on an (75)As-NMR study on the Fe-pnictide high-T(c) superconductor Y(0.95)La(0.05)FeAsO(1-y) (Y(0.95)La(0.05)1111) with T(c)=50 K that includes no magnetic rare-earth elements. The measurement of the nuclear-spin lattice-relaxation rate (75)(1/T(1)) has revealed that the nodeless bulk superconductivity takes place at T(c)=50 K while antiferromagnetic spin fluctuations develop moderately in the normal state. These features are consistently described by the multiple fully gapped s(±)-wave model based on the Fermi-surface nesting. Incorporating the theory based on band calculations, we propose that the reason that T(c)=50 K in Y(0.95)La(0.05)1111 is larger than T(c)=28 K in La1111 is that the Fermi-surface multiplicity is maximized, and hence the Fermi-surface nesting condition is better than that in La1111.
authors.affiliation: Graduate School of Engineering Science, Osaka University, Osaka 560-8531, Japan. mukuda@mp.es.osaka-u.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Mukuda
authors.forename: S
authors.initials: S
authors.lastname: Furukawa
authors.forename: H
authors.initials: H
authors.lastname: Kinouchi
authors.forename: M
authors.initials: M
authors.lastname: Yashima
authors.forename: Y
authors.initials: Y
authors.lastname: Kitaoka
authors.forename: P M
authors.initials: PM
authors.lastname: Shirage
authors.forename: H
authors.initials: H
authors.lastname: Eisaki
authors.forename: A
authors.initials: A
authors.lastname: Iyo