Observation of charge density wave characteristics in conducting polymer nanowires: Possibility of Wigner crystallization

We have presented here results of a low temperature transport study of polypyrrole nanowires having low electron densities, which shows characteristics of charge density waves observed in structurally ordered materials. The current-voltage characteristics of all these nanowires show a power-law dependence on voltage and temperature and a ``gap'' that decreases rapidly as the temperature is increased, confirming the existence of a long-range electron-electron interaction in the nanowires. A switching transition to highly conducting state has been observed above a threshold voltage, which can be tuned by changing the diameters of the nanowires and the temperature. Negative differential resistance and enhancement of noise have been observed above the threshold. These experimental results give evidence in favor of Wigner crystallization in these nanowires.