BaOsO$_3$: A Hund's metal in the presence of strong spin-orbit coupling

TL;DR

This study combines DFT and DMFT to analyze BaOsO$_3$, revealing it as a moderately correlated Hund's metal influenced by strong spin-orbit coupling, with a complex phase diagram including metallic and insulating states.

Contribution

It provides a detailed theoretical investigation of BaOsO$_3$, highlighting the interplay of Hund's metal behavior and strong spin-orbit coupling using advanced computational methods.

Findings

BaOsO$_3$ is a Hund's metal with moderate correlations.

Spin-orbit coupling suppresses electronic correlations.

The material remains metallic at physical coupling values.

Abstract

We investigate the 5d transition metal oxide BaOsO$_3$ within a combination of density functional theory (DFT) and dynamical mean-field theory (DMFT), using a matrix-product-state impurity solver. BaOsO$_3$ has 4 electrons in the t$_{2g}$ shell akin to ruthenates but stronger spin-orbit coupling (SOC) and is thus expected to reveal an interplay of Hund's metal behavior with SOC. We explore the paramagnetic phase diagram as a function of SOC and Hubbard interaction strengths, identifying metallic, band (van-Vleck) insulating and Mott insulating regions. At the physical values of the two couplings we find that BaOsO$_3$ is still situated inside the metallic region and has a moderate quasiparticle renormalization $m^*/m \approx 2$; consistent with specific heat measurements. SOC plays an important role in suppressing electronic correlations (found in the vanishing SOC case) through the splitting of a van-Hove singularity (vHs) close to the Fermi energy, but is insufficient to push the material into an insulating van-Vleck regime. In spite of the strong effect of SOC, BaOsO$_3$ can be best pictured as a moderately correlated Hund's metal.