Muon-spin-relaxation study of the relationship between the spin correlation and superconductivity in iron-based and high-Tc cuprate superconductors

为了研究自旋相关与超导性之间的关系，我们利用掺杂铁基超导体Fe1-y(Co,Ni,Zn)ySe0.3Te0.7和掺杂电子的高tc铜Pr1.3-xLa0.7CexCuO4+d的高质量单晶进行了介子自旋弛豫测量。在Fe1-y(Co,Ni,Zn)ySe0.3Te0.7中发现了杂质诱导的自旋相关的发展，表明轨道波动是电子对的粘合。在Pr1.3-xLa0.7CexCuO4+d中，发现在低温下超导性与短程磁序共存。这种新的共存现象可以用包含强电子相关的能带图来理解。由此得出结论，在铜酸盐中，自旋相关对超导性的出现起重要作用，而在铁基超导体中，自旋相关对超导性的出现影响不大。

In order to investigate the relationship between the spin correlation and superconductivity, we have performed muon-spin-relaxation measurements using high-quality single crystals of the impurity-substituted iron-based superconductor Fe1-y(Co,Ni,Zn)ySe0.3Te0.7 and of the electron-doped high-Tc cuprate Pr1.3-xLa0.7CexCuO4+d. Impurity-induced development of the spin correlation has been found in Fe1-y(Co,Ni,Zn)ySe0.3Te0.7, suggesting the orbital fluctuations as a glue of electron pairs. In Pr1.3-xLa0.7CexCuO4+d, it has been found that the superconductivity coexists with a short-range magnetic order at low temperatures. This novel coexistence can be understood in terms of the band picture including the strong electron correlation. Accordingly, it has been concluded that in cuprates, the spin correlation plays an important role on the appearance of superconductivity and that in iron-based superconductors, the appearance of the superconductivity is not so affected by the spin correlation.