Self-consistent DFT + DMFT Study of Strongly Correlated Electron Systems: Infinite Layer Rare-earth Nickelates

Novel materials whose properties are influenced by the presence of strongly correlated d- and/or f-electrons have been of sustained interest. Among these, the infinite-layer nickelates, RNiO2 (R = Nd, Pr, La), that exhibit superconductivity upon hole-doping, have received considerable attention. Based on self-consistent density functional theory (DFT) + embedded dynamical mean-field theory (eDMFT) calculations, we provide new insights into the physics of the low-energy many-body states of the parent compounds of the infinite layer systems. To appeal to a broad audience, we first elucidate the basic ideas underlying the self-consistent DFT+ eDMFT approach. Then we present results of our calcuations in the paramagnetic and magnetic states of RNiO2. We depict the emergent many-body states, and the associated correlation (U) and temperature (T) scales in a proposed U-T phase diagram. The key features are a low-T Fermi liquid (FL) phase, a high-T Curie-Weiss regime, and an antiferromagnetic phase in a relatively small U-T region. We associate the onset of the FL phase with partial screening of Ni-d electron moments; however, full screening occurs at lower temperatures. This may be related to insufficiency of conduction electrons to effectively screen the Ni-d moments, suggestive of Nozieres Exhaustion Principle. Consistent with the lack of experimental evidence for long-range magnetic order, and recent observation of magnetic excitations in NdNiO2, our results are suggestive of RNiO2 being in the paramagnetic state close to an antiferromagnetic dome, making magnetic fluctuations feasible. This may be consequential for superconductivity. In the end we briefly discuss our more recent work on doped nickelates.