First-order transition to a metallic state in polyacetylene: A strong-coupling polaronic metal

We present a theory of the first-order transition to the metallic state in polyacetylene in terms of a crossover from a lattice of charged solitons to a regular array of polaronlike distortions. The polaronic metal is shown to have a strong indirect attractive interaction, ${\mathrm{U}}^{\mathrm{*}}$≃-2Δ/3, between electrons in the half-filled, narrow, polaron subband within the Peierls energy gap (${\mathrm{E}}_{\mathrm{g}}$=2Δ).