Extended Hubbard Model with Unconventional Pairing in Two Dimensions

TL;DR

This paper rigorously proves that a two-dimensional extended Hubbard model with attraction exhibits unconventional pairing ground states with unique properties, depending on interaction parameters, and also discusses magnetic order in a special case.

Contribution

The paper provides a rigorous proof of unconventional pairing ground states in a 2D extended Hubbard model with attraction, including their uniqueness and dependence on interaction parameters.

Findings

Unconventional pairing ground states exist for any electron filling.

Ground states are unique and exhibit anisotropic pairing symmetry.

Special case shows Ising-type Nél order at half-filling without hopping.

Abstract

We rigorously prove that an extended Hubbard model with attraction in two dimensions has an unconventional pairing ground state for any electron filling. The anisotropic spin-0 or anisotropic spin-1 pairing symmetry is realized, depending on a phase parameter characterizing the type of local attractive interactions. In both cases the ground state is unique. It is also shown that in a special case, where there are no electron hopping terms, the ground state has Ising-type N\'eel order at half-filling, when on-site repulsion is furthermore added. Physical applications are mentioned.