Interchain Coulomb interactions in polyacetylene

The difference in the $\pi$ electron-electron interaction energy between charge-density waves in and out of phase on two parallel trans-polyacetylene chains is calculated up to second order in perturbation theory. It is found that this interaction favors the in-phase configuration, leading to a confinement potential when a soliton-antisoliton pair is present on the same chain. The confinement potential is found to go as $\frac{e^{-\frac{\pi d}{a}}}{d^3\sqrt{\frac{\pi d}{a}}}$, where $d$ is the interchain separation and $a$ the undimerized lattice spacing. The confinement potential is calculated to be 0.15 K/site for a pair of chains.