Isotope effect on the transition temperature Tc in Fe-based superconductors: The current status

Abstract

The results of the Fe isotope effect (Fe–IE) on the transition temperature Tc obtained up to date in various Fe-based high temperature superconductors are summarized and reanalyzed by following the approach developed in [R. Khasanov, M. Bendele, A. Bussmann-Holder, H. Keller, Phys. Rev. B 82, 212505 (2010)]. It is demonstrated that the very controversial results for Fe–IE on Tc are caused by small structural changes occurring simultaneously with the Fe isotope exchange. The Fe–IE exponent on Tc [αFe = − (ΔTc/Tc)/(ΔM/M), M is the isotope mass] needs to be decomposed into two components with the one related to the structural changes (αFestr) and the genuine (intrinsic one, αFeint). The validity of such decomposition is further confirmed by the fact that αFeint coincides with the Fe–IE exponent on the characteristic phonon frequencies αFeph as is reported in recent EXAFS and Raman experiments.