"Superconductor"-insulator transitions in a Hubbard chain with nearest- neighbor and bond-charge interactions

Abstract

We consider a half-filled generalized Hubbard chain with electron-hole symmetric correlated hopping and on-site and nearest-neighbor repulsions U and V respectively. In addition to the insulating charge- and spin-density wave phases for large V and U respectively, we identify a phase with dominant superconducting correlations at large distances for small U and V. Using two Berry phases (one associated to the charge and the other to the spin degrees of freedom) as discrete order parameters, we construct a phase diagram for the three thermodynamic phases.