EXTENDED STATES IN INTERACTING DISORDERED POLYACETYLENELIKE CHAINS

In spite of the enormous amount of theoretical and experimental work o n conducting polymers, the actual mechanism involved in the transition to a metallic regime is still an open and polemical question. Recentl y, Galvao et al. have proposed, based on the study of long, disordered , one-dimensional chains, that disorder is in the origin of the metall ic transition in conducting polymers. They suggest that disorder induc es the appearance of extended (conducting) states near the Fermi level . Since in actual samples there are interactions among chains, one imp ortant question is whether this kind of state could survive when inter actions among chains are taken into account in the calculations. In th is work we show that extended states can exist even when the interacti on among chains is taken implicitly into account. These results strong ly support disorder as the physical mechanism behind the metallic tran sition in conducting polymers. The density of states of long chains wa s obtained through the use of the negative factor counting technique c oupled to a tight-binding Hamiltonian.