Bipolaron transport in doped conjugated polymers

Interchain hopping of bipolarons (doubly charged defects) is discussed as a mechanism for spinless conductivity in doped polyacetylene, doped $\mathrm{poly}(p-\mathrm{p}\mathrm{h}\mathrm{e}\mathrm{n}\mathrm{y}\mathrm{l}\mathrm{e}\mathrm{n}\mathrm{e})$, and other doped polymers. It is shown that this mechanism can account for the observed dopant-concentration dependence of the conductivity in trans-polyacetylene and the observation of anomalously low magnetic susceptibilities in the highly conducting regime of several doped polymers.