Misc

In a history of superconductors 1911-2017, Fe-based superconductor ReFePnO1-xFx (Re: rare earth, Pn: Pnictogen) exhibits relative high superconducting transition temperatures (Tc)  58 K under ambient pressure. Electron doping by substitution of O2- with F- was required for appearance of a superconducting phase with high Tc. The Tc and upper critical field of ReFePnO1-xFx are very attractive for applications as superconducting wires and tapes under high magnetic fields, although demonstration of practical superconducting wires is a tough challenge due to the difficulty in controlling the F contents during a processing for ex-situ powder in tube method. In 2017, Zhang et al reported that iron-based superconducting tapes with Cu sheath showed superconducting electrical current (Jc) ~ 18 kAcm2. It is noteworthy that the tapes are sintered at 300 deg. C.

After obtaining my doctorate in engineering from Keio University, I spent five years as a researcher at the Tokyo Institute of Technology, Suzukakedai Campus in Yokohama. During that time, I made the first report on a material system called iron-based high-temperature superconductors (Fe-SCs). Research on Fe-SCs is still hot topic in condensed matter physics. Now, I am continuing my research mainly on the fabrication of superconducting wire using Fe-SCs, while being distracted by some traditional affairs as a member of the faculty. Research on Fe-SCs has encouraged young researchers towards the further discovery of novel layered superconductors. This article was prepared by updating the content of “A Private Story, Discovery of Iron-based High Tc Superconductors” previously published in the membership journal of the Physical Society of Japan.