Magnetism of the low-dimensional orbital-selective Mott insulators

The magnetic properties of low-D iron-based superconductors belonging to the 122 (Rb_xFe_ySe₂) and 123 (BaFe₂Se₃) families [1-2] proved to be a challenge for the theoretical description. Investigation of the orbital-selective Mott phase in 1D (relevant for 123 family) [3,4] revealed the existence of an exotic block spin order, namely AFM coupled FM spin islands. In parallel, inelastic neutron scattering experiments on quasi-1D BaFe₂Se₃ [2] and 2D Rb_xFe_ySe₂ [1] confirmed the relevance of these spin-block phases. The theoretical description of the latter requires long-range interaction and strong dimerization if within spin-wave models. In our work [4,5] we show that the magnetic properties of the orbital-selective Mott phase can be properly described by (short-range) multiorbital Hubbard models. Furthermore, we argue that the electronic correlations of itinerant orbitals are important for block-magnetism and that the minimal model which properly captures such a physics is the generalized Kondo-Heisenberg model.

[1] M. Wang, et al., Nature Comm. 2, 580 (2011)
[2] M. Mourigal, et al., Phys. Rev. Lett. 115, 047401 (2015)
[3] J. Rincon et al., Phys. Rev. Lett. 112, 106405 (2014)
[4] J. Herbrych, et al., Nat. Commun. 9, 3736 (2018)
[5] J. Heverhagen, et al., In preparation