Is there a proximate antiferromagnetic insulating phase in infinite-layer nickelates?*

We provide a set of computational experiments based on ab initio calculations to elucidate whether a cuprate-like antiferromagnetic insulating state can be present in the phase diagram of the infinite-layer nickelate family (RNiO₂, R= rare-earth). We show that metallicity in the parent phase is produced by an R-d band that requires hybridization with the Ni-d bands to become largely dispersive. If this off-plane R-Ni coupling is suppressed, the system is an antiferromagnetic insulator with an electronic structure closer to the nominal Ni⁺:d⁹ occupation since that largely dispersive band becomes much more localized away from the Fermi level. This can be achieved if a structural element that suppresses the c-axis dispersion is introduced (i.e. vacuum in a monolayer of NdNiO₂, or a blocking layer in multilayers formed by (NdNiO₂)₁/(NdNaO₂)₁). More importantly, we also show how the reduced Ruddlesden-Popper counterparts (e.g. R₄Ni₃O₈) are able to produce the same effect due to the presence of fluorite RO₂ blocking slabs

These results agree with the broad picture that it is possible to span the whole phase diagram of the cuprates within the nickelate family, which has profound implications for superconductivity in both types of materials.