Extended states in interacting disordered polyacetylenelike chains

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Abstract
In spite of the enormous amount of theoretical and experimental work on conducting polymers, the actual mechanism involved in the transition to a metallic regime is still an open and polemical question. Recently, Galvão et al. have proposed, based on the study of long, disordered, one-dimensional chains, that disorder is in the origin of the metallic transition in conducting polymers. They suggest that disorder induces the appearance of extended (conducting) states near the Fermi level. Since in actual samples there are interactions among chains, one important question is whether this kind of state could survive when interactions among chains are taken into account in the calculations. In this work we show that extended states can exist even when the interaction among chains is taken implicitly into account. These results strongly support disorder as the physical mechanism behind the metallic transition in conducting polymers. The density of states of long chains was obtained through the use of the negative factor counting technique coupled to a tight-binding Hamiltonian.