Strain-induced tuning of the electronic Coulomb interaction in 3d transition metal oxide perovskites

TL;DR

This study investigates how epitaxial strain affects the effective Coulomb interactions in transition metal oxide perovskites, revealing material-dependent variations in Hubbard U and Hund's J through first-principles calculations.

Contribution

It provides the first systematic analysis of strain effects on Coulomb interactions in different d-shell occupation oxides using constrained RPA calculations.

Findings

U increases with tensile strain in LaTiO3

U decreases with tensile strain in LaCrO3

LaVO3 exhibits intermediate behavior

Abstract

Epitaxial strain offers an effective route to tune the physical parameters in transition metal oxides. So far, most studies have focused on the effects of strain on the bandwidths and crystal field splitting, but recent experimental and theoretical works have shown that also the effective Coulomb interaction changes upon structural modifications. This effect is expected to be of paramount importance in current material engineering studies based on epitaxy-based material synthesization. Here, we perform constrained random phase approximation calculations for prototypical oxides with a different occupation of the d shell, LaTiO3 (d1), LaVO3 (d2), and LaCrO3 (d3), and systematically study the evolution of the effective Coulomb interactions (Hubbard U and Hund's J) when applying epitaxial strain. Surprisingly, we find that the response upon strain is strongly dependent on the material. For LaTiO3, the interaction parameters are determined by the degree of localization of the orbitals, and grow with increasing tensile strain. In contrast, LaCrO3 shows the opposite trends: the interactions parameters shrink upon tensile strain. This is caused by the enhanced screening due to the larger electron filling. LaVO3 shows an intermediate behavior.