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

摘要

It has been argued that the very high transition temperatures of the highestTc cuprate superconductors are facilitated by enhanced CuO2 plane couplingthrough the (Bi,Tl,Hg)-O intermediary layers. Whether enhanced coupling throughintermediary layers can also influence Tc in the iron arsenide superconductorshas never been tested due the lack of appropriate systems for study. Here wereport the crystal structures and properties of two iron arsenidesuperconductors, Ca10(Pt3As8)(Fe2As2)5 (the 10-3-8 phase) andCa10(Pt4As8)(Fe2As2)5 (the 10-4-8 phase). Based on -Ca-(PtnAs8)-Ca-Fe2As2-layer stacking, the most important difference in the structures lies in thestructural and electronic characters of the intermediary platinum arsenidelayers. Electron doping through partial substitution of Pt for Fe in the Fe2As2layers leads to Tc of 11 K in the 10-3-8 phase and 25 K in the 10-4-8 phase.Using the chemical concepts of Zintl ion electron counting and the stability ofPt in the 5d8 configuration we argue that the dramatic difference in Tc arisesbecause the intermediary layer is semiconducting in the 10-3-8 phase butmetallic in the 10-4-8 phase, leading to enhanced interlayer coupling in the10-4-8 phase. The results suggest that metallic intermediary layers may offer anew road to higher Tc in iron arsenide superconductors.