Phase-diagram of correlated electrons in a lattice of berry phase molecules

A model for correlated electrons in a lattice with local additional spin-1 degrees of freedom inducing constrained hopping is studied both in the low density limit and at quarter filling. We show that in both 1D and 2D two particles form a bound state even in the presence of a repulsive U<Uc. A picture of a dilute Bose gas, leading to off-diagonal long-range order (LRO) in 2D (quasi-LRO in 1D), is supported by quantitative calculations in 1D which allow for a determination of the phase diagram.