  On examining the stability of a Wigner Crystal (WC) in an ionic dielectric,
two competitive effects due to Polaron formation are found to be important: (i)
the screening of the Coulomb forces which destabilizes the crystal, compensated
by (ii) the increase of the carrier mass (polaron mass). The quantum melting of
the Polaron Wigner Crystal (PWC) is examined. By calculating the quantum
fluctuations of both the electrons and the polarization, we show that there is
a competition between the dissociation of the Polarons at the
insulator-to-metal transition (IMT), and a melting towards a polaron liquid. We
find that at strong coupling ($\alpha > \alpha^*$), a liquid state of polarons
cannot exist, and the IMT is driven by polaron dissociation. Next, we show that
the dipolar interactions between localized polarons are responsible for a
phonon instability of the PWC as the density increases. This provides a new
mechanism for the IMT in doped dielectrics. Examining the sign of the
dielectric constant of the PWC, we conjecture that such an instability could
yield an Insulator-to-Superconductor transition.
