title: Superconductivity at 52 K in hydrogen-substituted LaFeAsO(1-x)Hx under high pressure.
abstract: The 1111-type iron-based superconductor LnFeAsO(1-x)Fx (Ln stands for lanthanide) is the first material with a Tc above 50 K, other than cuprate superconductors. Electron doping into LaFeAsO by H, rather than F, revealed a double-dome-shaped Tc-x diagram, with a first dome (SC1, 0.05<x<0.20) and a second dome (SC2, 0.2<x<0.5). Here, we report the Tc for the whole hydrogen-doping range in LaFeAsO(1-x)Hx under pressures of up to 19 GPa. Tc rises to 52 K at 6 GPa for the Tc-valley composition between the two Tc domes. This is the first instance of the Tc exceeding 50 K in La-1111-type iron-based superconductors. On the other hand, the Tc of SmFeAsO1-x)Hx decreased continually, keeping its single-dome structure up to 15 GPa. The present findings strongly suggest that t(he main reason for realization of the Tc >50 K observed in RE-1111 compounds (RE: Pr, Sm, and Gd) at ambient pressure is the merging of SC1 and SC2.
authors.affiliation: Department of Physics, College of Humanities and Sciences, Nihon University, Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: Department of Physics, College of Humanities and Sciences, Nihon University, Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Soeda
authors.affiliation: Department of Physics, College of Humanities and Sciences, Nihon University, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nukii
authors.affiliation: Department of Physics, College of Humanities and Sciences, Nihon University, Tokyo, Japan.
authors.forename: C
authors.initials: C
authors.lastname: Kawashima
authors.affiliation: Department of Physics, School of Science and Technology for Future Life, Tokyo Denki University, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Nakanishi
authors.affiliation: Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Iimura
authors.affiliation: Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Muraba
authors.affiliation: Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Matsuishi
authors.affiliation: 1] Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama, Japan [2] Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Hosono