Cooperative effects of Jahn-Teller distortion, magnetism, and Hund's coupling in the insulating phase of ${\mathrm{BaCrO}}_3$

We employ a combination of density functional theory and dynamical mean-field theory to investigate the electronic structure of the recently synthesized insulator ${\mathrm{BaCrO}}_3$. Our calculations show that Hund's coupling is responsible for strong correlation effects, which are however not sufficient to turn the system insulating without breaking any symmetry. The Hund's correlated metal is however unstable with respect to orbital ordering, which indeed makes the system insulating. The orbitally ordered insulator favors Jahn-Teller distortions and a secondary magnetic ordering.

Figure 1

Quasiparticle weight $Z$ as a function of $U$ fixing the ratio $J{}_h/U$ fixed to the value 0.155 calculated with ED solver. Inset: Resolved orbital density of state of Wannier orbitals (DFT) and DMFT calculations.

Figure 2

Orbitally-resolved spectral density for $U=3.5\mathrm{eV}$, $J_h=0.505\mathrm{eV}$ in G-type OO for the undistorted tetragonal unit cell of ${\mathrm{BaCrO}}_3$ (results from CTQMC).

Figure 3

Total energy gain calculated within DFT in the nonmagnetic (NM) and C-type magnetic structure and within $\mathrm{DFT}+\mathrm{U}$ in the C-type magnetic structure as function of the Jahn-Teller distortion $\delta$ (difference between long/short Cr-O bonds).

Figure 4

Resolved orbital spectral density for $U=3.25\mathrm{eV}$, $J_h=0.505\mathrm{eV}$ in G-type OO for $\delta =0.17\AA$. Lower panel shows results using the ED solver, the upper panel results from CTQMC. Inset: Orbital arrangement (G-type OO) in the plane of tetragonal unit cell with the two inequivalent Cr-O distances.

Figure 5

Orbitally-resolved spectral density for $U=3.25\mathrm{eV}$, $J_h=0.505\mathrm{eV}$ in G-type orbital ordering and C-type spin ordering for $\delta =0.17\text{Å}$. Lower two panels: Results using the ED solver for majority/minority spin channels. Upper two panels: Results from CTQMC for majority/minority spin channels. Inset: Spin (C-type AFM) and orbital (G-type OO) arrangement in the plane of tetragonal unit cell with the two inequivalent Cr-O distances.