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Iron-based superconductors display a variety of magnetic phases originating in the
competition between electronic, orbital, and spin degrees of freedom. Previous theoretical
investigations of the multi-orbital Hubbard model in one-dimension revealed the existence
of an orbital-selective Mott phase (OSMP) with block spin order [1,2,3]. Recent inelastic
neutron scattering (INS) experiments on the BaFe 2 Se 3 ladder compound confirmed the
relevance of the block-OSMP. Moreover, the powder INS spectrum revealed an unexpected
structure, containing both low-energy acoustic and high-energy optical modes [5]. Here we
present the theoretical prediction for the dynamical spin structure factor within a block-
OSMP regime using the density-matrix renormalization-group method [4]. In agreement with
experiments, we find two dominant features: low-energy dispersive and high-energy
dispersionless modes. We argue that the former represents the spin-wave-like dynamics of
the block ferromagnetic islands, while the latter is attributed to a novel type of local on-site
spin excitations controlled by the Hund coupling.
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Dagotto, Phys. Rev. E 93, 063313, (2016).
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Communications volume 9, Article number: 3736 (2018).
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Broholm , Phys. Rev. Lett. 115, 047401 (2015). |