Charge order from the local Coulomb repulsion in undoped infinite-layer nickelates

A charge order with a wave vector q~(1/3,0,0) observed by recent experiments in undoped infinite-layer nickelates, which is very different from that in hole-doped cuprates, demands a theoretical explanation. Here we employ density-functional-theory and dynamical-mean-field-theory calculations and show that a charge ordered state of Ni¹⁺-Ni²⁺-Ni¹⁺ pattern can have a lower total energy than the uniform paramagnetic state and usual checkerboard antiferromagnetic state in a prototypical nickelate NdNiO₂. It arises because of the presence of conduction bands near the Fermi energy. Under a large Coulomb repulsion on the Ni-dx2-y2 orbitals, the electron on one of the Ni-ion is transferred to the conduction bands, which not only enhances the self-doping effect but also drives the electrons on the other two Ni-dx2-y2 orbitals to become more localized. We further show that the stability and stripe pattern of the charge ordered state can be controlled by the charge transfer energy between Ni-dx2-y2 and conduction bands, which is beyond the famous Zaanen-Sawatzky-Allen classification scheme. Our work highlights the multi-band and strongly correlated nature of infinite-layer nickelates and reveals some unique properties of nickelates that are distinct from cuprates.