  We investigated the ionic Hubbard model with mass imbalance in one dimension,
using the density matrix renormalization group method. This model exhibits a
band insulator phase and an antiferromagnetic one, both with a finite spin gap.
We found that this quantum phase transition is continuous, unalike the previous
mean-field theory result. The von Neumann block entropy is maximum at the
critical points, a fact that we used to build the phase diagram.
