Dielectric catastrophe at the Mott transition

We study the Mott transition as a function of interaction strength in the half-filled Hubbard chain with next-nearest-neighbor hopping t' by calculating the response to an external electric field using the density matrix renormalization group. The electric susceptibility chi diverges when approaching the critical point from the insulating side. We show that the correlation length xi characterizing this transition is directly proportional to fluctuations of the polarization and that chi approximately xi2. The critical behavior shows that the transition is infinite order for all t', whether or not a spin gap is present, and that hyperscaling holds.