A single polymer chain as an organic quantum wire: optical evidence of a purely 1D density of states

The excitonic luminescence of an isolated polydiacetylene polymer chain in its monomer matrix is studied by micro-photoluminescence. These chains behave as perfect 1D semiconducting wires with the expected 1/$\sqrt{E}$ density of states between 5 and 50 K. The temperature dependence of the homogeneous width is explained by interaction with longitudinal acoustic phonons of the crystal in the range of temperature explored. The optical phonons of the chain which are involved in the vibronic transitions are found to have coherence times ranging from 300 to 600 fs.