Emergence of a potential charge disproportionated insulating state in SrCrO${}_3$

Abstract

We use a combination of density functional theory (DFT) and dynamical mean-field theory (DMFT) to investigate the potential emergence of a charge-disproportionated insulating phase in SrCrO${}_3$, whereby the Cr cations disproportionate according to $3{\text{Cr}}^{4+}\to 2{\text{Cr}}^{3+}+{\text{Cr}}^{6+}$ and arrange in ordered planes perpendicular to the cubic [111] direction. We show that the charge disproportionation couples to a structural distortion where the oxygen octahedra around the nominal Cr${}^{6+}$ sites contract, while the octahedra surrounding the Cr${}^{3+}$ sites expand and distort. Our results indicate that the charge-disproportionated phase can be stabilized for realistic values of the Hubbard $U$ and Hund's $J$ parameters, but this requires a scaling of the DFT+DMFT double counting correction by at least 35%. The disproportionated state can also be stabilized in DFT+U calculations for a specific magnetic configuration with antiparallel magnetic moments on adjacent Cr${}^{3+}$ sites and no magnetic moment on the Cr${}^{6+}$ sites. While this phase is higher in energy than other magnetic states that can arise in SrCrO${}_3$, the presence of an energy minimum suggests that the charge disproportionated state represents a metastable state of SrCrO${}_3$.

10 pages, 8 figures