High Tc electron doped Ca10(Pt3As8)(Fe2As2)5 and Ca10(Pt4As8)(Fe2As2)5 superconductors with skutterudite intermediary layers

摘要

It has been argued that the very high transition temperatures of the highest Tc cuprate superconductors are facilitated by enhanced CuO2 plane coupling through heavy metal oxide intermediary layers. Whether enhanced coupling through intermediary layers can also influence Tc in the new high Tc iron arsenide superconductors has never been tested due the lack of appropriate systems for study. Here we report the crystal structures and properties of two iron arsenide superconductors, Ca10(Pt3As8)(Fe2As2)5 (the “10-3-8 phase”) and Ca10(Pt4As8)(Fe2As2)5 (the “10-4-8 phase”). Based on -Ca-(PtnAs8)-Ca-Fe2As2- layer stacking, these are very similar compounds for which the most important differences lie in the structural and electronic characteristics of the intermediary platinum arsenide layers. Electron doping through partial substitution of Pt for Fe in the FeAs layers leads to Tc of 11 K in the 10-3-8 phase and 26 K in the 10-4-8 phase. The often-cited empirical rule in the arsenide superconductor literature relating Tc to As-Fe-As bond angles does not explain the observed differences in Tc of the two phases; rather, comparison suggests the presence of stronger FeAs interlayer coupling in the 10-4-8 phase arising from the two-channel interlayer interactions and the metallic nature of its intermediary Pt4As8 layer. The interlayer coupling is thus revealed as important in enhancing Tc in the iron pnictide superconductors.