Early quantum models included a soliton pair creation model by Maki and a proposal by John Bardeen that condensed CDW electrons tunnel coherently through a tiny pinning gap, fixed at ± k F unlike the Peierls gap. Maki's theory lacked a sharp threshold field and Bardeen only gave a phenomenological interpretation of the threshold field. However, a 1985 paper by Krive and Rozhavsky pointed out that nucleated solitons and antisolitons of charge ± q generate an internal electric field E* proportional to q/ε. The electrostatic energy (1/2) ε [ E ± E* ] prevents soliton tunneling for applied fields E less than a threshold E T = E* /2 without violating energy conservation. Although this Coulomb blockade threshold can be much smaller than the classical depinning field, it shows the same scaling with impurity concentration since the CDW's polarizability and dielectric response ε vary inversely with pinning strength.