摘要：The 1111-type iron-based superconductor Ln FeAsO1-xFx ( Ln stands for lanthanide) is the first material with a T c above 50 K, other than cuprate superconductors. Electron doping into LaFeAsO by H, rather than F, revealed a double-dome-shaped T c- x diagram, with a first dome (SC1, 0.05 T c for the whole hydrogen-doping range in LaFeAsO1-xHx under pressures of up to 19 GPa. T c rises to 52 K at 6 GPa for the T c-valley composition between the two T c domes. This is the first instance of the T c exceeding 50 K in La-1111-type iron-based superconductors. On the other hand, the T c of SmFeAsO1- x H x decreased continually, keeping its single-dome structure up to 15 GPa. The present findings strongly suggest that the main reason for realization of the T c >50 K observed in RE-1111 compounds (RE: Pr, Sm, and Gd) at ambient pressure is the merging of SC1 and SC2.
