Rigorous results on superconducting ground states for attractive extended Hubbard models

TL;DR

This paper rigorously proves that certain extended Hubbard models with attractive interactions have a superconducting ground state, specifically the Yang eta-paired state, under broad conditions including any dimension and band filling.

Contribution

It provides a rigorous proof that the Yang eta-paired state is the exact ground state for a class of extended Hubbard models with attractive interactions.

Findings

Ground state is the Yang eta-paired state for these models.

Superconducting ground state is rigorously established.

Results apply to any dimension, lattice type, and band filling.

Abstract

We show that the exact ground state for a class of extended Hubbard models including bond-charge, exchange, and pair-hopping terms, is the Yang "eta-paired" state for any non-vanishing value of the pair-hopping amplitude, at least when the on-site Coulomb interaction is attractive enough and the remaining physical parameters satisfy a single constraint. The ground state is thus rigorously superconducting. Our result holds on a bipartite lattice in any dimension, at any band filling, and for arbitrary electron hopping.