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，我们用高质量的杂质替代铁基超导体Fe1-y(Co，Ni，Zn)ySe0.3Te0.7和电子掺杂的高T_c铜酸盐Pr1.3-xLa0.7CexCuO4+d进行了介子自旋弛豫测量，发现在Fe1-y(Co，Ni，Zn)ySe0.3Te0.7中杂质诱导了自旋关联的发展，表明轨道涨落是电子对的粘合剂。在Pr1.3-xLa0.7CexCuO4+d中，超导电性在低温下以短程磁序共存。这种新颖的共存可以用包含强电子关联的能带图来理解。由此得出结论：在铜酸盐中，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，超导电性的出现不受自旋关联的影响。

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.