Superconductivity at 52 K in hydrogen-substituted LaFeAsO1-xHx under high pressure

TL;DR

This study demonstrates that applying high pressure to hydrogen-substituted LaFeAsO1-xHx significantly increases its superconducting transition temperature to 52 K, surpassing 50 K for the first time in this class of materials.

Contribution

It reveals that high pressure induces the merging of two superconducting domes in LaFeAsO1-xHx, leading to a Tc exceeding 50 K, a novel finding in iron-based superconductors.

Findings

Tc reaches 52 K at 6 GPa in LaFeAsO1-xHx.

High pressure causes the merging of two Tc domes in LaFeAsO1-xHx.

Tc remains below 50 K in SmFeAsO1-xHx under similar conditions.

Abstract

The 1111-type iron-based superconductor LnFeAsO1-xFx (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 LaFeAsO1-xHx 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-xHx decreased continually, keeping its single-dome structure up to 15 GPa. The present findings strongly suggest that the 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.