Strain-induced heteronuclear charge disproportionation in EuMnO$_3$

TL;DR

This paper introduces the concept of heteronuclear charge disproportionation in complex oxides, demonstrating how pressure and strain can induce a transition in EuMnO$_3$ from Eu$^{3+}$Mn$^{3+}$O$_3$ to a novel Eu$^{2+}$Mn$^{4+}$O$_3$ phase, with potential for discovering new physics.

Contribution

It proposes and computationally investigates heteronuclear charge disproportionation, a new mechanism involving charge transfer between different elements on distinct sites, in EuMnO$_3$ under pressure and strain.

Findings

Pressure and strain can induce a phase transition in EuMnO$_3$.

Identification of measurable signatures for experimental detection.

Prediction of other candidate materials for heteronuclear charge disproportionation.

Abstract

Charge disproportionation transitions in complex oxides most commonly link high-temperature phases containing identical cations with the same oxidation state and crystallographic site, to low-temperature phases in which charge transfer between these ions results in unequal oxidation states. Here we propose, based on density functional calculations, a related concept that we term \textit{heteronuclear} charge disproportionation, in which charge transfer occurs between different elements on different crystallographic sites. We show for the case of EuMnO$_3$ that such a transition from the experimentally observed Eu$^{3+}$Mn$^{3+}$O$_3$ phase to the so far unknown Eu$^{2+}$Mn$^{4+}$O$_3$ phase can be triggered by pressure and epitaxial strain. We then identify measurable signatures to aid in an experimental exploration of the complex pressure- and biaxial strain-dependent phase stability of EuMnO$_3$ that we hope to motivate with our predictions. We suggest other candidate crystal chemistries for heteronuclear charge disproportionation, in which novel physics could emerge from the coexistence of instabilities.