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 $cl{c}_{\mathrm{cr}}$ the electrons form pinned (chaotic) soliton states; at $cg{c}_{\mathrm{cr}}$ the solitons form an unpinned conducting lattice. We find ${c}_{\mathrm{cr}}=\frac{{a}^{2}}{{\ensuremath{\pi}}^{2}{{l}_{0}}^{2}}$, where ${l}_{0}$ is the width of the solitons. The theory may explain the metal-insulator transition observed in doped polyacetylene at ${c}_{\mathrm{cr}}\ensuremath{\sim}1$%.