Theory of Metal-Insulator Transition in Peierls Systems with Nearly Half-Filled Bands

Abstract

It is shown that a metal-insulator transition takes place in a Peierls system with half-filled bands at a critical concentration, $c_{\mathrm{cr}}$, of excess electrons. At $c<\mathrm{}{c}_{\mathrm{cr}}$ the electrons form pinned (chaotic) soliton states; at $c>\mathrm{}{c}_{\mathrm{cr}}$ the solitons form an unpinned conducting lattice. We find $c_{\mathrm{cr}}=\frac{a^2}{{\pi }^2{l_0}^2}$, where $l_0$ is the width of the solitons. The theory may explain the metal-insulator transition observed in doped polyacetylene at $c_{\mathrm{cr}}\sim 1$%.