Laboratoire de Physique Théorique
Toulouse - UMR 5152

We study the quantum phase transition from an insulator to a metal in the ground state of the half-filled t-t’ repulsive Hubbard model. using the continuum-limit bosonization approach and density matrix renormalization group calculations. An effective low-energy Hamiltonian that describes the insulator-metal transition is derived. We find that the gross features of the phase diagram are well-described by the standard theory of commensurate-incommensurate transitions in a wide range of parameters. We also obtain an analytical expression for the insulator-metal transition line t’c(U,t). In the presence of a staggered ionic potential ∆, we find that, for particular values of the next-nearest-hopping amplitude t’, with increasing on-site repulsion, at Uc1 the model shows a transition from a band insulator into a metallic state and at larger Uc2 there is a transition from a metal into a ferroelectric insulator.