Abstract
We derive an effective three-orbital model for the infinite-layer nickelates based on the band structure obtained by the GW approximation (GWA), where we consider the Ni 3dx2−y2 and O 2p orbitals forming the σ-bond. In the GWA, the self-energy correction to the local density approximation (LDA) increases the energy difference between Ni 3dx2−y2 and O 2p, which reduces the bandwidth of the antibonding 3dx2−y2 orbitals. The isolation of the Ni 3dx2−y2 around the Fermi level suppresses the screening effect. As a result, the correlation effect becomes more significant than that in the model constructed by the LDA-based downfolding. Furthermore, the Mott-Hubbard type character is enhanced in the GWA-based effective model, because the charge-transfer energy increases more rapidly compared to the increase in the interaction parameters.
Highlights
The discovery of nickel superconductors [1] has attracted renewed attention to superconductivity in strongly correlated electron systems [2,3,4,5,6,7]
We find that the GW approximation (GWA)-based effective model is predicted to be more strongly-correlated with enhanced Mott-Hubbard type character
Given that the differences in the band structure between the density functional theory (DFT)/local density approximation (LDA) and that in the GWA are commonly seen in transition metal oxides where 3d and 2p orbitals with different correlation strengths coexist near the Fermi level, it would be of great interest to derive an effective low-energy model for infinite-layer nickelates based on the GWA
Summary
The discovery of nickel superconductors [1] has attracted renewed attention to superconductivity in strongly correlated electron systems [2,3,4,5,6,7]. To improve the accuracy of the parameters in the low-energy model, we can replace the Green’s function (G0) constructed from the DFT/LDA eigenenergies with the dressed Green’s function in the GW approximation (GWA).1 Such a derivation based on the GWA has been recently performed for the celebrated cuprate superconductors [37, 38]. Given that the differences in the band structure between the DFT/LDA and that in the GWA are commonly seen in transition metal oxides where 3d and 2p orbitals with different correlation strengths coexist near the Fermi level, it would be of great interest to derive an effective low-energy model for infinite-layer nickelates based on the GWA. We mainly focus on the dpp three-orbital models (single-orbital model is discussed in Appendix) because it is interesting to investigate how the GWA modifies the charge-transfer energy
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