title: Inverse iron isotope effect on the transition temperature of the (Ba,K)Fe2As2 superconductor.
abstract: We report that the (Ba,K)Fe(2)As(2) superconductor (transition temperature, T(c) approximately 38 K) has an inverse iron isotope coefficient alpha(Fe) = -0.18(3) (where T(c) approximately M(-alphaFe) and M is the iron isotope mass); i.e., the sample containing the large iron isotope mass depicts a higher T(c). Systematic inverse shifts in T(c) were clearly observed between the samples using three types of Fe isotopes ((54)Fe, natural Fe, and (57)Fe). This indicates the first evidence of the inverse isotope effect in high-T(c) superconductors. This anomalous mass dependence on T(c) implies an exotic coupling mechanism in Fe-based 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: Kunihiro
authors.initials: K
authors.lastname: Kihou
authors.forename: Kiichi
authors.initials: K
authors.lastname: Miyazawa
authors.forename: Chul-Ho
authors.initials: CH
authors.lastname: Lee
authors.forename: Hijiri
authors.initials: H
authors.lastname: Kito
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Eisaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Yanagisawa
authors.forename: Yasumoto
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Akira
authors.initials: A
authors.lastname: Iyo