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

为了研究自旋关联与超导电性之间的关系，我们用高质量的掺杂铁基超导体Fe_（1-y）（Co，Ni，Zn）_ySe_（0.3）Te_（0.7）和电子掺杂的高Tc铜酸盐Pr_（1.3-x）La_（0.7）CexCuO_（4 +d）单晶进行了μ子自旋弛豫测量。在Fe_（1-y）（Co，Ni，Zn）_ySe_（0.3）Te_（0.7）中发现了由杂质引起的自旋关联的发展，表明轨道涨落是电子对的粘合剂。在Pr_（1.3-x）La_（0.7）Ce_xCuO_（4 +d）中，发现低温下超导性与短程磁序共存。这种新的共存可以理解的能带图片，包括强电子相关。因此，在铜氧化物中，自旋关联对超导电性的出现起着重要的作用，而在铁基超导体中，自旋关联对超导电性的出现影响不大。

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.