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The properties of AMO3 perovskite oxides, where M is a 3d transition metal, depend strongly on the level of covalency between the metal d and oxygen p orbitals. With their complex spin orders and metal-insulator transition, rare-earth nickelates verge between dominantly ionic and covalent characters. Accordingly, the nature of their ground state is highly debated. Here, we reconcile the ionic and covalent visions of the insulating state of nickelates. Through first-principles calculations, we show that it is reminiscent of the ionic charge disproportionation picture (with strictly low-spin 4+ and high-spin 2+ Ni sites) while exhibiting strong covalence effects with oxygen electrons shifted toward the depleted Ni cations, mimicking a configuration with identical Ni sites. Our results further hint at strategies to control electronic and magnetic phases of transition metal oxide perovskites.
The rare-earth nickelates are a rich playground for transport properties, known to host non-Fermi liquid character, resistance saturation and metal-insulator transitions. We report a study of transport in LaNiO3 in the presence of tunable disorder in
Based on the electronic band structure obtained from first principles DFT calculations, the opticalspectra of yttrium and neodymium nickelates are computed. We show that the results are in fairagreement with available experimental data. We clarify th
Whilst electron correlations were previously recognized to trigger beyond conventional direct current (DC) electronic transportations (e.g. metal-to-insulator transitions, bad metal, thermistors), their respective influences to the alternation curren
Anisotropies in electronic transportations conventionally originate from the nature of low symmetries in crystal structures, and were not anticipated for perovskite oxides, the crystal asymmetricity of which is far below, e.g. van der Waals or topolo
We show that charge ordering (more precisely, two-sublattice bond disproportionation) in the rare earth nickelate perovskites is intimately related to a negative charge transfer energy. By adding an additional potential on the Ni d states we are able