First-principles Studies for the Hydrogen Doping Effects on Iron-based Superconductors

TL;DR

This study uses first-principles calculations to investigate how hydrogen doping enhances the superconducting transition temperature in LaFeAsO_(1-y) by inducing structural distortions and electron doping effects.

Contribution

It provides a detailed atomic-level understanding of hydrogen's role in improving superconductivity in iron-based materials, which was previously not well understood.

Findings

Hydrogen stabilizes near iron atoms, attracting negatively charged FeAs layers.

Hydrogen doping causes lattice shrinkage and structural distortion favorable for higher Tc.

Hydrogen acts as an electron dopant, shifting the Fermi level.

Abstract

We study hydrogen doping effects in an iron-based superconductor LaFeAsO_(1-y) by using the first-principles calculation and explore the reason why the superconducting transition temperature is remarkably enhanced by the hydrogen doping. The present calculations reveal that a hydrogen cation stably locating close to an iron atom attracts a negatively-charged FeAs layer and results in structural distortion favorable for further high temperature transition. In fact, the lattice constant a averaged over the employed supercell shrinks and then the averaged As-Fe-As angle approaches 109.74 degrees with increasing the hydrogen doping amount. Moreover, the calculations clarify electron doping effects of the solute hydrogen and resultant Fermi-level shift. These insights are useful for design of high transition-temperature iron-based superconductors.