Hierarchies of stability regions for η-pairing superconducting ground states of generalized Hubbard models
Abstract:For a class of generalized one dimensional Hubbard models, we study the stability region for the superconducting η-pairing ground state. We exploit the Optimum 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. The phenomenon is explained by studying the properties of certain exact eigenstates of the OGS Hamiltonians.