Dual nature of the ferroelectric and metallic state in LiOsO$_3$

TL;DR

This study uses density functional theory to explore the dual ferroelectric and metallic properties of LiOsO$_3$, revealing how specific orbital behaviors underpin its unique state.

Contribution

It uncovers the dual nature of LiOsO$_3$'s ferroelectric and metallic states and links lattice instabilities to orbital hybridizations, providing new insights into ferroelectric metals.

Findings

Ferroelectric instability linked to Li-O modes

Metallic response mainly from t$_{2g}$ orbitals

Strong correlation effects in half-filled t$_{2g}$ orbitals

Abstract

Using density functional theory we investigate the lattice instability and electronic structure of recently discovered ferroelectric metal LiOsO$_3$. We show that the ferroelectric-like lattice instability is related to the Li-O distortion modes while the Os-O displacements change the d-p hybridization as in common ferroelectric insulators. Within the manifold of the d-orbitals, a dual behavior emerges. The ferroelectric transition is indeed mainly associated to the nominally empty e$_g$ orbitals which are hybridized with the oxygen p orbitals, while the t$_{2g}$ orbitals are responsible of the metallic response. Interestingly, these orbitals are nominally half-filled by three electrons, a configuration which suffers from strong correlation effects even for moderate values of the screened Coulomb interaction.