Solitons in Polyacetylene Produced and Probed by Positive Muons

Abstract

Positive muons were injected into both trans- and cis-${\left(\mathrm{CH}\right)}_x$ as well as ${\left(\mathrm{CD}\right)}_x$. A marked difference was found in the field dependence of the muon spin-relaxation functions between cis- and trans-polyacetylene. A quantitative explanation was obtained by considering the unpaired electron produced by a muon: It is localized at the nearby carbons in cis-polyacetylene forming a radical state; on the other hand, in trans-polyacetylene, it becomes highly mobile and takes a one-dimensional solitonlike motion as clearly indicated by the inverse-root field dependence found for the relaxation rates.