Binding energy of the Wannier exciton on an organic quantum wire

The exciton on a single polydiacetylene chain is considered in a Wannier approach, taking into account the surrounding polarizable medium. The electron-hole Coulomb interaction potential is explictly obtained for a quantum wire of circular cross-section, and numerically calculated for a rectangular one. The predicted binding energy and Bohr radius, starting from the chain conformation, are in good agreement with experimental values. This shows the importance of considering the monomer matrix embedding the chain, and the major role of confinement, together with electron correlations, for describing the exciton. The method is general and applicable to any quantum wire.