An efficient method for strongly correlated electrons in one dimension

TL;DR

This paper demonstrates that the Piris natural orbital functional 7 (PNOF7) effectively models strongly correlated electrons in one-dimensional systems, including hydrogen chains and the Hubbard model, with high accuracy across various regimes and system sizes.

Contribution

The study introduces and validates the PNOF7 method for accurately describing non-dynamic correlation effects in 1D strongly correlated electron systems.

Findings

PNOF7 accurately models 1D Hubbard systems across different fillings.

PNOF7 maintains accuracy for large systems with up to 122 electrons.

Results compare well with density-matrix renormalization group calculations.

Abstract

The one-particle reduced density matrix functional theory in its natural orbital functional (NOF) version is used to study strongly correlated electrons. We show the ability of the Piris NOF 7 (PNOF7) to describe non-dynamic correlation effects in one-dimensional (1D) systems. An extensive study of 1D systems that includes Hydrogen (H) chains and the 1D Hubbard model with periodic boundary conditions is provided. Different filling situations and large sizes with up to 122 electrons are considered. Compared to quasi-exact results, PNOF7 is accurate in different correlation regimes for the 1D Hubbard model even away from the half-filling, and maintains its accuracy when the system size increases. The symmetric and asymmetric dissociations of the linear H chain composed of 50 atoms are described to remark the importance of long-range interactions in presence of strong correlation effects. Our results compare remarkably well with those obtained at the density-matrix renormalization group level of theory.