Theoretical investigation of excitonic magnetism in LaSrCoO${}_4$

Abstract

We use the LDA+U approach to search for possible ordered ground states of LaSrCoO${}_4$. We find a staggered arrangement of magnetic multipoles to be stable over a broad range of Co $3d$ interaction parameters. This ordered state can be described as a spin-denity-wave-type condensate of $d_{xy}\otimes d_{x^2-y^2}$ excitons carrying spin $S=1$. Further, we construct an effective strong-coupling model, calculate the exciton dispersion and investigate closing of the exciton gap, which marks the exciton condensation instability. Comparing the layered LaSrCoO${}_4$ with its pseudo cubic analog LaCoO${}_3$, we find that for the same interaction parameters the excitonic gap is smaller (possibly vanishing) in the layered cobaltite.

6 pages, 6 figures

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Cited by in corpus (4)

• Excitonic dispersion of the intermediate-spin state in LaCoO${}_3$ revealed by resonant inelastic X-ray scattering
• Damping of spinful excitons in LaCoO${}_3$ by thermal fluctuations: Theory and experiment
• Ferromagnetism of LaCoO${}_3$ films
• Pressure-induced spin-state ordering in Sr${}_2$CoO${}_3$F