Exact demonstration of η pairing in the ground state of an attractive-UHubbard model

Abstract
We show that the recently discovered η-pairing scheme combined with the Nagaoka-Thouless picture for itinerant ferromagnetism leads to a new type of superconductivity in the attractive-U Hubbard model in the sector 0<(N-N)/(N+N)≪1, where N and N are the occupation numbers of up and down spins. This results holds for all dimensionalities d≥2.