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

摘要

We study hydrogen doping effects in an iron-based superconductorLaFeAsO_(1-y) by using the first-principles calculation and explore the reasonwhy the superconducting transition temperature is remarkably enhanced by thehydrogen doping. The present calculations reveal that a hydrogen cation stablylocating close to an iron atom attracts a negatively-charged FeAs layer andresults in structural distortion favorable for further high temperaturetransition. In fact, the lattice constant a averaged over the employedsupercell shrinks and then the averaged As-Fe-As angle approaches 109.74degrees with increasing the hydrogen doping amount. Moreover, the calculationsclarify electron doping effects of the solute hydrogen and resultantFermi-level shift. These insights are useful for design of hightransition-temperature iron-based superconductors.