Osmates on the verge of a Hund's-Mott transition: The different fates of NaOsO$_3$ and LiOsO$_3$

TL;DR

This paper investigates why NaOsO$_3$ and LiOsO$_3$, despite their similarities, exhibit vastly different spectroscopic behaviors by analyzing their proximity to a Hund's-Mott insulating phase using first-principles many-body methods.

Contribution

It reveals that the different properties of these compounds are due to their proximity to a Hund's-Mott transition influenced by intraorbital repulsion and Hund's exchange.

Findings

NaOsO$_3$ and LiOsO$_3$ are near a Hund's-Mott insulating phase.

Small material differences cause sharp changes in electronic mobility.

The physics is driven by cooperative intraorbital repulsion and Hund's exchange.

Abstract

We clarify the origin of the strikingly different spectroscopic properties of the chemically similar compounds NaOsO$_3$ and LiOsO$_3$. Our first-principle many-body analysis demonstrates that the highly sensitive physics of these two materials is controlled by their proximity to an adjacent Hund's-Mott insulating phase. In mildly correlated $5d$ oxides, this physics is triggered by the {\sl cooperative} action of intraorbital repulsion and Hund's exchange in half-filled $t_{2g}$ outer-shells. Small material-specific details hence result in an extremely sharp change of the electronic mobility, explaining the surprisingly different properties of the paramagnetic high-temperature phases of the two compounds.