Nonlinear dynamics of an added carrier in trans-polyacetylene in the presence of an electric field

In the absence of electric field, an electron or hole added to a trans-polyacetylene chain without a neutral soliton distorts the chain to form a large polaron. When an electric field is applied after polaron formation, we find that, depending on the magnitude of the electric field, two qualitatively different pictures of polaron evolution are realized. In fields E≤106 V/cm, the polaron exhibits an instability with respect to decay into a pair of solitons, although completion of the transformation process may require much longer conjugation length than is available in typical samples. In higher fields, however, the polaron dissolves into a free electron and a phonon-type lattice deformation. We discuss and compare the energetics of these two processes.