Dynamical correlations across the spin-state transition in LaCoO$_3$
L. Craco and E. M\"uller-Hartmann

The electronic properties of ${\rm LaCoO_3}$ across the spin-state transition are studied using the LDA+DMFT method. Combining the LDA band structure of the ${\rm Co}$~$3d$ orbitals in the low-spin state with multi-orbital DMFT for $U=5~{\rm eV}$, 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 {\it spin-state crossover} due to large dynamical renormalizations of the energy splitting between the $t_{2g}$ and $e_g$ manifold. 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 multi-orbital 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.

© 2008 The American Physical Society.