Interchain coupling and optical absorption in degenerate and nondegenerate polymers

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Abstract
We present a numerical study based on an extended Su-Schrieffer-Heeger model of the effects of interchain coupling on both degenerate and nondegenerate conjugated polymers. In particular, we study polaronic and bipolaronic excitations and examine their delocalization (spread over more than one chain) as a function of the coupling strength. It is shown that there is a discontinuous change in the degree of delocalization at a critical value of the coupling. We also study the influence of delocalization on the optical absorption and show that, in the polaron case, the relative strength of spectral lines in the absorption gap below the interband transitions is changed dramatically from the behavior predicted for independent chains.