Fernández Afonso J, Sotnikov A, Kuneš J
Institute of Solid State Physics, TU Wien, Wiedner Hauptstr. 8, 1020 Vienna, Austria.
J Phys Condens Matter. 2018 Apr 4;30(13):135603. doi: 10.1088/1361-648X/aab0bb. Epub 2018 Feb 20.
We use the LDA+U approach to search for possible ordered ground states of LaSrCoO. 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-density-wave-type condensate of [Formula: see text] 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 with its pseudo cubic analog LaCoO, we find that for the same interaction parameters the excitonic gap is smaller (possibly vanishing) in the layered cobaltite.
