Melting of a Wigner crystal in an ionic dielectric

The melting of a Wigner Crystal of electrons placed into a host polar mater ial is examined as a function of the density and the temperature. When the coupling to the longitudinal optical modes of the host medium is turned on, the WC is progressively transformed into a polaronic Wigner crystal. We es timate the critical density for crystal melting at zero temperature using t he Lindeman criterion. We show that above a certain critical value of the F rohlich electron-phonon coupling, the melting towards a quantum liquid of p olarons is not possible, and the insulator-to-metal transition is driven by the ionization of the polarons (polaron dissociation). The phase diagram a t finite temperature is obtained by making use of the same Lindeman criteri on. Results are also provided in the case of an anisotropic electron band m ass, sheering that the scenario of polaron dissociation can be relevant in anisotropic compounds such as the superconducting cuprates at rather modera te e-ph couplings.