We investigate the transition to the insulating state in the one-dimensional Hubbard model with bond-charge interaction x (Hirsch model), at half-filling and T= 0. By means of the density-matrix renormalization group algorithm the charge gap closure is examined by both standard finite-size scaling analysis and looking at singularities in the derivatives of single-site entanglement. The results of the two techniques show that a quantum phase transition takes place at a finite Coulomb interaction u c (x) for x≳ 0.5. The region 0< u< u c turns out to have a superconducting nature, at least for not too large x> x c.
American Physical Society
16 Feb 2006
Volume: 73 Issue: 8 Pages: 085113
Physical Review B