Polaron-bipolaron—soliton doping in polyacetylene

We have performed a self-consistent numerical study, which allows each CH group in a finite polyacetylene chain to relax to its equilibrium position, in order to investigate the formation of the polaron, soliton, and soliton lattice in the framework of Su-Schrieffer-Heeger model. The bondalternation order parameter, the delocalization of the gap states, the polaron-formation energy, the soliton-formation energy, the Peierls gap, and the gap separating the valence (or condition) band and the impurity band are calculated as functions of dopant level. The effect of electron-electron interaction is then examined in the Hartree approximation. Our results are compared with those derived by other authors. Although our approach simulates a doping process, further calculation based on the decaying of an electron-hole pair into a soliton-antisoliton pair gives exactly the same results as those shown in this paper. In particular, our finding clearly demonstrates the singlecharge injection via polarons which subsequently combine to form soliton-antisoliton pairs, in agreement with the recent experimental discovery.