Superconductivity and wire fabrication of FeSe family

The 11 family is an fascinating iron-based superconducting system for not only elucidation of superconducting mechanism but also technological applications because of the simplest crystal structures, the less toxic and high critical field. Recently, we found that the superconductivity appears in the specimen immersed in alcoholic beverages. Focused on the pressure dependence of Se height from Fe layer in FeSe, we found that the Tc is correlated to Se height. Moreover, the anion height dependence of $T_{c}$ for all FeAs-based superconductor obeyed a universal curve with a peak around 1.38 {\AA}. We succeeded in observing the transport $J_{c}$ in the single- and 7-core wires of FeTe$_{x}$Se$_{1-x}$ superconductor using an in-situ powder-in-tube (PIT) method. The $J_{c}$ values in single- and 7-core wire are as high as 159 A/cm$^{2}$ and 100 A/cm$^{2}$ at 4.2 K, respectively. It is considered that the optimization of the composition, together with the improvement of the grain boundary in FeTe$_{x}$Se$_{1-x}$ superconducting wires, will lead to higher $J_{c}$.