Types of single particle symmetry breaking in transition metal oxides due to electron correlation

TL;DR

This paper investigates electron correlation effects in small transition metal oxides, revealing that left-right correlations between metal and oxygen atoms are significant and involve off-diagonal two-electron hopping terms comparable to Hubbard interactions.

Contribution

It introduces a detailed wave function analysis showing the dominant electron correlation types and their manifestation as off-diagonal two-electron hopping terms in transition metal oxides.

Findings

Left-right electron correlation dominates in these molecules.

Off-diagonal two-electron hopping terms are comparable to Hubbard interactions.

Correlation effects are mediated by excitations into antibonding and d-type orbitals.

Abstract

Very accurate wave functions are calculated for small transition metal oxide molecules. These wave functions are decomposed using reduced density matrices to study the underlying correlation of electrons. The correlation is primarily of left-right type between the transition metals and the oxygen atoms, which is mediated by excitations from the nominal single Slater ground state into antibonding and d-type orbitals. In a localized representation, this correlation manifests itself in a 2-electron hopping term that is off-diagonal. This term is of similar magnitude to the commonly considered Hubbard-type on-site interaction.