A charge model as an effective model of one-dimensional Hubbard and extended Hubbard systems: its application to linear optical spectrum calculations in large systems based upon many-body Wannier functions

TL;DR

This paper introduces a charge model for one-dimensional Hubbard systems that accurately predicts optical spectra in large systems, demonstrating effective spin-charge separation even at intermediate interaction strengths.

Contribution

The study develops a charge model compatible with charge fluctuations, extending the applicability of spin-charge separation concepts to intermediate interaction regimes.

Findings

The charge model reproduces original spectra well in the intermediate U region.

Optical conductivity spectra are accurately determined using many-body Wannier functions.

Spin-charge separation remains effective at intermediate U values.

Abstract

We propose an effective model called the "charge model", for the half-filled one-dimensional Hubbard and extended Hubbard models. In this model, spin-charge separation, which has been justified from an infinite on-site repulsion ($U$) in the strict sense, is compatible with charge fluctuations. Our analyses based on the many-body Wannier functions succeeded in determining the optical conductivity spectra in large systems. The obtained spectra reproduce the spectra for the original models well even in the intermediate $U$ region of $U=5-10T$, with $T$ being the nearest-neighbor electron hopping energy. These results indicate that the spin-charge separation works fairly well in this intermediate $U$ region against the usual expectation and that the charge model is an effective model that applies to actual quasi-one-dimensional materials classified as strongly correlated electron systems.