Dynamical correlations leading to site and orbital selective Mott insulator transition in hydrogen doped SmNiO3

Electron doping induces metal-to-insulator transition (MIT) in ${\mathrm{SmNiO}}_{3}$ as realized by experiments. While earlier density functional theory (DFT) studies with static correlations fell short of explaining the recent MIT observations at lower hydrogen concentrations, we present a comprehensive computational investigation employing an advanced approach. We combine DFT with dynamical mean field theory $(\mathrm{DFT}+\mathrm{DMFT})$ to efficiently analyze the insulating behavior of hydrogen-doped ${\mathrm{SmNiO}}_{3}$. In contrast to previous theoretical works, our calculations predict an insulator transition occurring at a reduced doping level of H:Ni = 0.5:1. Specifically, while the $\mathrm{DFT}+U$ method reveals a gap opening between $p\text{\ensuremath{-}}\mathrm{to}\text{\ensuremath{-}}d$ orbitals, the DMFT approach highlights a gap opening between $d\text{\ensuremath{-}}\mathrm{to}\text{\ensuremath{-}}d$ orbitals. Our findings uncover a selective Mott transition in site and orbital characteristics, with the Ni ions proximate to the doped hydrogen exhibiting Mott-like traits. Notably, DMFT calculations highlight a pronounced dependence on Hund's parameter $J$, implying the presence of Hundness in the Mott insulator. This study underscores the necessity of accounting for dynamical correlations to accurately describe the electronic structure of strongly correlated electron-doped rare-earth nickelates.