Orbital-Selective Mott Transition and Evolution of the Zhang-Rice State in Cubic Phase UO$_{2}$ Under Pressure

TL;DR

This study combines advanced computational methods to reveal an orbital-selective Mott transition in cubic UO₂ under pressure, showing specific electronic state evolutions and the disappearance of the Zhang-Rice state.

Contribution

It provides the first ab initio prediction of an orbital-selective Mott transition in UO₂ and details the evolution of electronic states under pressure.

Findings

Orbital-selective Mott insulator-metal transition at ~45 GPa

j=5/2 states become metallic while j=7/2 remain insulating up to 60 GPa

Rapid decrease of 5f occupation and Zhang-Rice state disappearance after transition

Abstract

We study the electronic structure of cubic phase uranium dioxide at different volumes using a combination of density functional theory and dynamical mean-field theory. The \emph{ab initio} calculations predict an orbital-selective Mott insulator-metal transition at a moderate pressure of $\approx 45$ GPa. At this pressure the $j=5/2$ states become metallic, while the $j=7/2$ states remain insulating up to about 60 GPa. In the metallic state, we observe a rapid decrease of the 5$f$ occupation and total angular momentum with pressure. Simultaneously, the generalized Zhang-Rice state, which is of predominantly $j=5/2$ character, quickly disappears after the transition into the metallic phase.