Maximal Stability Regions for Superconducting Ground States of Generalized Hubbard Models

TL;DR

This paper identifies the maximal parameter regions where superconducting eta-pairing ground states are stable in generalized Hubbard models, using advanced computational methods to derive precise conditions for superconductivity.

Contribution

It introduces an improved approach combining the OGS method and Lanczos diagonalization to determine stability boundaries and necessary conditions for eta-pairing superconductivity.

Findings

Identified asymptotic stability boundary segments independent of cluster size.

Derived necessary and sufficient conditions for superconductivity in these models.

Explained superconductivity phenomena via properties of exact eigenstates.

Abstract

For a class of generalized Hubbard models, we determine the maximal stability region for the superconducting eta-pairing ground state. We exploit the Optimized Ground State (OGS) approach and the Lanczos diagonalization procedure to derive a sequence of improved bounds. We show that some pieces of the stability boundary are asymptotic, namely independent on the OGS cluster size. In this way, necessary and sufficient conditions are obtained to realize superconductivity in terms of an eta-pairing ground state. The phenomenon is explained by studying the properties of certain exact eigenstates of the OGS hamiltonians.