High-density electron doping of SmNiO$_3$ from first principles

TL;DR

This study uses first-principles calculations to explore how high-density electron doping induces a Mott transition in SmNiO$_3$, revealing electron localization effects and gap opening in the electronic structure.

Contribution

It provides a detailed first-principles analysis of electron doping effects on SmNiO$_3$, highlighting the localizing behavior and electronic structure changes associated with the Mott transition.

Findings

Added electrons localize on NiO$_6$ octahedra

Doping induces a large gap between Ni $e_g$ orbitals

Electronic evolution is similar for different doping methods

Abstract

Recent experimental work has realized a new insulating state of samarium nickelate (SmNiO$_3$), accessible in a reversible manner via high-density electron doping. To elucidate this behavior, we use the first-principles density functional theory (DFT) + U method to study the effect of added electrons on the crystal and electronic structure of SmNiO$_3$. First, we track the changes in the crystal and electronic structure with added electrons compensated by a uniform positive background charge at concentrations of $\frac{1}{4}$, $\frac{1}{2}$, $\frac{3}{4}$, and 1 electrons per Ni. The change in electron concentration does not rigidly shift the Fermi energy; rather, the added electrons localize on NiO$_6$ octahedra causing an on-site Mott transition and a change in the density of states resulting in a large gap between the occupied and unoccupied Ni $e_g$ orbitals at full doping. This evolution of the density of states is essentially unchanged when the added electrons are introduced by doping with interstitial H or Li ions.