Dynamical correlations across the spin-state transition in $\mathrm{La}\mathrm{Co}{\mathrm{O}}_3$

The electronic properties of $\mathrm{La}\mathrm{Co}{\mathrm{O}}_3$ across the spin-state transition are studied using the $\mathrm{LDA}+\mathrm{DMFT}$ method. Combining the local density approximation band structure of the $\mathrm{Co}3d$ orbitals in the low-spin state with multiorbital dynamical mean field theory for $U=5\mathrm{eV}$, we investigate the evolution of the single-particle spectra at different spin states. We show that small differences in the orbital occupation can induce a smooth spin-state crossover due to large dynamical renormalizations of the energy splitting between the $t_{2g}$ and $e_g$ manifolds. We find large changes in the one-particle spectra that are unique fingerprints of each of the possible spin states. The key signature of the intermediate- and high-spin states is the presence of Hubbard satellites in the $t_{2g}$ spectral density. Further, our results for the paramagnetic metallic phase shows Kondo-like resonance in the $t_{2g}$ sector, indicating the role of multiorbital Kondo screening processes in the high-spin state. These results provide a theoretical basis for physics of room-temperature thermoelectric materials based on cobalt oxides.

Figure 1

(Color online) LDA partial density of states for the $e_g$ (dotted) and $t_{2g}$ (solid) orbitals in the LS state taken from Ref. 20.

Figure 2

(Color online) Partial density of states of the $t_{2g}$ orbitals for $U=5.0\mathrm{eV}$ in the low-spin (solid), intermediate-spin (dotted), and high-spin (dot dashed) states of $\mathrm{La}\mathrm{Co}{\mathrm{O}}_3$.

Figure 3

(Color online) Partial density of states of the $e_g$ orbitals for $U=5.0\mathrm{eV}$ in the low-spin (solid), intermediate-spin (dotted), and high-spin (dot dashed) states of $\mathrm{La}\mathrm{Co}{\mathrm{O}}_3$.

Figure 4

(Color online) Low-$T$ $3d$ $\mathrm{LDA}+\mathrm{DMFT}$ total density of states in the low-spin (solid), intermediate-spin (dotted), and high-spin (dot dashed) states of $\mathrm{La}\mathrm{Co}{\mathrm{O}}_3$.

Figure 5

(Color online) Partial density of states of the $t_{2g}$ orbitals in the high-spin state for $U=5.0\mathrm{eV}$ and different temperatures.

Figure 6

(Color online) Comparison of theoretical $\mathrm{LDA}+\mathrm{DMFT}$ (IPT) calculations for the unoccupied part of the total one-electron spectral function at different spin-state phases of $\mathrm{La}\mathrm{Co}{\mathrm{O}}_3$ to the experimental results taken from Ref. 1 for XAS. The intensity of the experimental curves is normalized to coincide with theory.