Excitonic magnetism in $d^6$ perovskites

Abstract

We use the LDA+U method to study the possibility of exciton condensation in perovskites of transition metals with $d^6$ electronic configuration such as LaCoO${}_3$. For realistic interaction parameters we find several distinct solutions exhibiting spin-triplet exciton condensate, which gives rise to a local spin density distribution while the ordered moments are vanishingly small. Rhombohedral distortion from the ideal cubic structure suppresses the ordered state, contrary to the spin-orbit coupling which enhances the excitonic condensation energy. We explain the trends observed in the numerical simulations with the help of a simplified strong-coupling model. Our results indicate that LaCoO${}_3$ is close to the excitonic instability and suggest ways to make it order.

arXiv commentpublished version

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• LDA+DMFT approach to ordering phenomena and the structural stability of correlated materials
• Damping of spinful excitons in LaCoO${}_3$ by thermal fluctuations: Theory and experiment
• Excitonic magnet in external field: complex order parameter and spin currents
• Spin texture and spin current in excitonic phases of the two-band Hubbard model
• Theoretical investigation of excitonic magnetism in LaSrCoO${}_4$
• Mott-Enhanced Exciton Condensation in a Hubbard bilayer
• Quantum paramagnet near spin-state transition
• Pressure-induced spin-state ordering in Sr${}_2$CoO${}_3$F
• Ferromagnetic and insulating behavior of LaCoO3 films grown on a (001) SrTiO3 substrate. A simple ionic picture explained ab initio