title: Absence of an appreciable iron isotope effect on the transition temperature of the optimally doped SmFeAsO(1-y) Superconductor.
abstract: We report the iron (Fe) isotope effect on the transition temperature (T(c)) in oxygen-deficient SmFeAsO(1-y), a 50-K-class, Fe-based superconductor. For the optimally doped samples with T(c) = 54  K, a change of the average atomic mass of Fe (M(Fe)) causes a negligibly small shift in T(c), with the Fe isotope coefficient (α(Fe)) as small as -0.024 ± 0.015 (where α(Fe)=-d lnT(c)/dlnM(Fe)). This result contrasts with the finite, inverse isotope shift observed in optimally doped (Ba,K)Fe2As2, indicating that the contribution of the electron-phonon interaction markedly differs between these two Fe-based high-T(c) superconductors.
authors.affiliation: National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan. paras-shirage@aist.go.jp
authors.forename: Parasharam M
authors.initials: PM
authors.lastname: Shirage
authors.forename: Kiichi
authors.initials: K
authors.lastname: Miyazawa
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Kihou
authors.forename: Hijiri
authors.initials: H
authors.lastname: Kito
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Yoshida
authors.forename: Yasumoto
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Eisaki
authors.forename: Akira
authors.initials: A
authors.lastname: Iyo