Born Effective Charge Reversal and Metallic Threshold State at a Band Insulator-Mott Insulator Transition

N. Gidopoulos S. Sorella, E. Tosatti

We study the quantum phase transition between a band (``ionic'') insulator and a Mott-Hubbard insulator, realized at a critical value U=Uc in a bipartite Hubbard model with two ine…