The Fermion-ladder Models: Extensions of the Hubbard Model with $\eta$-pairing

TL;DR

This paper introduces extended fermion-ladder models with $ta$-pairing symmetry, including an exact solution for a new SU(4) model, advancing understanding of superconductivity mechanisms.

Contribution

It presents a new SU(4) fermion-ladder model with $ta$-pairing symmetry and provides an exact solution, extending previous models.

Findings

The SU(2|2) model matches the extended Hubbard model by Essler et al.

The new SU(4) model exhibits $ta$-pairing symmetry.

The SU(4) model can be solved exactly.

Abstract

We propose the two-leg fermion-ladder models for SU(2|2) and SU(4) cases. The former is exactly the extended Hubbard model proposed by Essler, Korepin and Schoutens. The later is a new model also with $\eta$-pairing symmetry which is important for superconductivity. This new extension of the Hubbard model can be solved exactly.