Abstract
Resonant Inelastic X-Ray Scattering (RIXS) experiments on the iron-based ladder BaFe2Se3 unveiled an unexpected two-peak structure associated with local orbital (dd) excitations in a block-type antiferromagnetic phase. A mixed character between correlated band-like and localized excitations was also reported. Here, we use the density matrix renormalization group method to calculate the momentum-resolved charge- and orbital-dynamical response functions of a multi-orbital Hubbard chain. Remarkably, our results qualitatively resemble the BaFe2Se3 RIXS data, while also capturing the presence of long-range magnetic order as found in neutron scattering, only when the model is in an exotic orbital-selective Mott phase (OSMP). In the calculations, the experimentally observed zero-momentum transfer RIXS peaks correspond to excitations between itinerant and Mott insulating orbitals. We provide experimentally testable predictions for the momentum-resolved charge and orbital dynamical structures, which can provide further insight into the OSMP regime of BaFe2Se3.
Highlights
Resonant Inelastic X-Ray Scattering (RIXS) experiments on the iron-based ladder BaFe2Se3 unveiled an unexpected two-peak structure associated with local orbital excitations in a block-type antiferromagnetic phase
By calculating the orbital response functions of the competing paramagnetic metal (PM) and FM insulator states, we show that block orbital-selective Mott phase (OSMP) has a characteristic two-peak structure that is distinctive and in striking agreement with RIXS results on BaFe2Se324
Our study strongly suggests that the ground state of BaFe2Se3 is an OSMP with block magnetic order
Summary
Resonant Inelastic X-Ray Scattering (RIXS) experiments on the iron-based ladder BaFe2Se3 unveiled an unexpected two-peak structure associated with local orbital (dd) excitations in a block-type antiferromagnetic phase. Inelastic neutron scattering data[23] is compatible with the exciting idea that BaFe2Se3 is in an orbital-selective Mott phase (OSMP) at ambient pressure[26–28], where one orbital is localized with a Mott gap while the others are gapless and itinerant (see Fig. 1). This state displays an exotic magnetic order involving 2 × 2 ferromagnetic blocks that are antiferromagnetically staggered. Here for the first time, we use the density matrix renormalization group (DMRG) technique to compute the momentum-resolved charge and orbital response functions, as well as the single-particle spectral function (at zero temperature), of the block magnetic OSMP of a multi-orbital Hubbard chain.
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