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arXiv · 1712.03774

Theoretical investigation of excitonic magnetism in LaSrCoO$_{4}$

J. Fernández Afonso·A. Sotnikov·J. Kuneš
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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.

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J. Fernández Afonso, A. Sotnikov, J. Kuneš. 2017-12-11. Theoretical investigation of excitonic magnetism in LaSrCoO$_{4}$. https://doi.org/10.1088/1361-648x%2Faab0bb

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