Evidence Against Solitons in Polyacetylene: Magnetic Measurements

Abstract

EPR and dc conductivity measurements in pristine and acceptor-doped cis-${(\mathrm{CH})}_{x}$ and pristine trans-${(\mathrm{CH})}_{x}$ are reported. At dopant concentrations of 0.7% and 0.9% As${\mathrm{F}}_{5}$, the cis isomer shows a Pauli susceptibility and a conductivity that seem to arise from randomly distributed, highly conducting regions---a sign of dopant aggregation. There in no need to invoke charged solitons. Comparison with previous experimental results suggests that they do not support the existence of charged solitons in the doped trans isomer; neutral solitons in the undoped trans isomer are also questioned.