Cation Order Control of Correlations in Double Perovskite Sr$_2$VNbO$_6$

TL;DR

This study uses advanced first-principles methods to explore how cation order influences electronic correlations and structure in the double perovskite Sr$_2$VNbO$_6$, revealing Hund's metallic behavior and correlation-driven structural effects.

Contribution

It provides the first detailed theoretical analysis of Sr$_2$VNbO$_6$, showing how cation order affects electronic correlations and structural properties using DFT+DMFT.

Findings

Electronic structure differs from parent compounds.

Electronic correlations influence crystal structure.

Emergence of Hund's metallic behavior.

Abstract

Double perovskites extend the design space for new materials, and they often host phenomena that don't exist in their parent perovskite compounds. Here, we present a detailed first principles study of the correlated double perovskite Sr$_2$VNbO$_6$, where inter-cationic charge transfer and strength of electronic correlations depend strongly on the cation order. By using Density Functional Theory + Embedded Dynamical Mean Field Theory, we show that this compound has a completely different electronic structure than either of its parent compounds despite V and Nb being from the same group in the periodic table. We explain how the electronic correlations' effect on the crystal structural parameters determines on which side of the Hund's metal-Mott insulator transition the material is. Our results demonstrate the emergence of Hund's metallic behavior in a double perovskite that has $d^1$ parents, and underlines the importance of electronic correlation effects on the crystal structure.