Escape mechanism of a self-trapped topological soliton

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The adiabatic minimum-energy path of a self-trapped topological soliton is computed for trans-polyacetylene using the Su-Schrieffer-Heeger Hamiltonian and ab initio methods. The frequently cited activation barrier via a ridge shift of the hypertangent order parameter overestimates its true value by 14 orders of magnitude. Self-trapped solitons migrate along the Goldstone mode direction with continuously adjusted amplitudes so that a small-width soliton expands and a large-width soliton shrinks when they move uphill. A soliton with the critical width may migrate without any amplitude modifications. In an open chain as solitons move from the chain center toward a chain edge, the minimum-energy path first follows a tilted washboard landscape and then increases exponentially at the edge.