AMPLITUDE MODE AROUND A MOVING SOLITON IN POLYACETYLENE

Amplitude mode around a moving soliton in polyacetylene is studied by the numerical simulations of the motion of the charged soliton in an external electric field within Su, Schrieffer and Heeger's model. Its shape is visualized by numerically subtracting the Goldstone mode from the time derivatives of the lattice displacements, which are thought to be decomposed into linear normal modes around the (moving) soliton. The frequency of the amplitude mode as a function of the soliton velocity is estimated from the oscillations of the soliton width and the lattice potential energy, the latter oscillation being considered to be induced mainly by the amplitude oscillation. The frequency is found to increase as the velocity deviates from zero.