Ab Initio Downfolding Based on the GW Approximation for Infinite-Layer Nickelates

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.

A single-band model with enhanced pairing from DMRG-based downfolding of the three-band Hubbard model

“…Here we demonstrate an alternative way to downfold the three-band Hubbard model based on a density-matrix renormalization group (DMRG) [55] construction of Cucentered Wannier functions. The general idea of constructing effective models using ab initio calculations has been explored in various contexts [56][57][58][59][60]. Our approach uses DMRG to compute the natural orbitals of the threeband model, and from those construct Wannier functions, similar to a recent work that downfolds hydrogen chains into Hubbard-like models [61].…”