Superconductivity in the repulsive Hubbard model

TL;DR

This paper reviews various methods used to study the 2D repulsive Hubbard model and introduces an improved variational approach that enhances the Gutzwiller ansatz, revealing consistent d-wave superconductivity near half filling.

Contribution

It presents a new variational many-electron state extending the Gutzwiller ansatz, offering improved accuracy in modeling superconductivity in the Hubbard model.

Findings

Superconductivity with d-wave symmetry is consistently observed near half filling.

The new variational state improves upon the Gutzwiller ansatz.

Multiple methods confirm the presence of superconductivity in the model.

Abstract

The two-dimensional repulsive Hubbard model has been investigated by a variety of methods, from small to large U. Superconductivity with d-wave symmetry is consistently found close to half filling. After a brief review of the various methods a variational many-electron state is discussed in more detail. This trial state is a natural extension of the Gutzwiller ansatz and provides a substantial improvement thereof.