Topotactic hydrogen in nickelate superconductors and akin infinite-layer oxides ABO2

TL;DR

This study uses density functional theory to investigate the stability of intercalated hydrogen in nickelate superconductors, revealing its potential role in their electronic properties and superconductivity.

Contribution

It provides the first computational analysis of topotactic hydrogen binding energies in nickelates, linking hydrogen intercalation to electronic structure changes.

Findings

Hydrogen intercalation is energetically favorable in LaNiO2 but not in Sr-doped NdNiO2.

Hydrogen presence transforms LaNiO2's electronic structure from a doped cuprate-like state to a two-orbital Mott insulator.

Topotactic hydrogen may explain the variability in superconductivity among nickelates.

Abstract

Superconducting nickelates appear to be difficult to synthesize. Since the chemical reduction of ABO3 (A: rare earth; B transition metal) with CaH2 may result in both, ABO2 and ABO2H, we calculate the topotactic H binding energy by density functional theory (DFT). We find intercalating H is energetically favorable for LaNiO2 but not for Sr-doped NdNiO2. This has dramatic consequences for the electronic structure as determined by DFT+dynamical mean field theory: that of 3d9 LaNiO2 is similar to (doped) cuprates, 3d8 LaNiO2H is a two-orbital Mott insulator. Topotactical H might hence explain why some nickelates are superconducting and others are not.