Exact Solution of a Hubbard Chain with Bond-Charge Interaction

TL;DR

This paper provides an exact solution for a Hubbard chain with bond-charge interaction, revealing a Mott transition at a specific interaction strength and indicating potential superconductivity near half filling.

Contribution

It presents the first exact solution of a Hubbard chain with bond-charge interaction under the condition t = X, elucidating its phase transition and ground state properties.

Findings

Mott transition occurs at U=4t at half filling.

Superconducting states are degenerate with metallic states near half filling.

Superconductivity is favored for small U with slight perturbations.

Abstract

We obtain the exact solution of a general Hubbard chain with kinetic energy $t$, bond-charge interaction $X$ and on-site interaction $U$ with the only restriction $t = X$. At zero temperature and half filling, the model exhibits a Mott transition at $U = 4t$. In the metallic phase and near half filling, superconducting states are part of the degenerate ground state and are favored for small $U$ if the system is slightly perturbed.