Daily Overview: Today’s highlighted work focuses on the correlated electronic structure of the three-band Emery model for CuO2/NiO2 planes in cuprates and nickelates and its downfolding to an effective single-band description. In [1], the authors employ a neural quantum state variational method based on hidden fermion determinant states (HFDS), first using matrix product states as a benchmark and then simulating fully two-dimensional systems up to 10×10 unit cells (300 sites), characterizing the momentum distribution of doped carriers, and finding an electron-hole dichotomy similar to that observed in cuprate experiments. More importantly, using interacting Wannier functions they downfold the three-band model into an effective single-band description, covering the cuprate charge-transfer regime, the nickelate Hubbard-Mott regime, and charge-transfer-gap scans. They find that the effective model deviates significantly from the conventional Fermi-Hubbard model: U/t is enhanced, some parameters exhibit pronounced doping dependence, and additional terms such as density-assisted hopping t_n appear. Among these, t_n makes the largest contribution to particle-hole asymmetry, rather than the next-nearest-neighbor hopping, and the effective parameters depend sensitively on the charge-transfer energy, doping, and interaction ratio. This work demonstrates that HFDS is an efficient tool for studying the two-dimensional Emery model and suggests that effective single-band descriptions of nickelate superconductivity may need to include new interaction terms generated by the underlying multiband model. arXiv submission processing window: 2026-09-30 00:00 to 2026-09-30 00:00 UTC.

1. Neural-quantum-state based downfolding of the three-band Emery model for cuprates and nickelates

Summary: This paper employs neural quantum states, in particular hidden fermion determinant states (HFDS), to perform a scalable variational study of the three-band Emery model for CuO2/NiO2 planes in cuprates and nickelates. The authors first benchmark against matrix product states on width-two geometries and then simulate fully two-dimensional systems up to 10×10 unit cells (300 sites), characterizing the momentum-space distribution of dopants and finding an electron-hole dichotomy similar to that observed in cuprate experiments. The study further downfolds the three-band model to an effective single-band description by constructing interacting Wannier functions, with parameters covering the cuprate charge-transfer regime, the nickelate Hubbard-Mott regime, and scans of the charge-transfer gap. The results show that the effective model deviates significantly from the usual Fermi-Hubbard model: U/t is enhanced, some parameters exhibit pronounced doping dependence, and important terms beyond the conventional Hubbard model emerge, most notably the density-assisted hopping t_n; moreover, t_n makes the largest contribution to particle-hole asymmetry, rather than next-nearest-neighbor hopping. The effective parameters depend sensitively on the charge-transfer energy, doping, and interaction ratio. The conclusion is that HFDS is an efficient tool for studying the two-dimensional Emery model, and that a single-band description may need to include new interaction terms generated by the underlying multiband model.