Fano Factor Reduction on the 0.7 Conductance Structure of a Ballistic One-Dimensional Wire

We have measured the nonequilibrium current noise in a ballistic one-dimensional wire which exhibits an additional conductance plateau at $0.7\times 2e^2/h$. The Fano factor shows a clear reduction on the 0.7 structure, and eventually vanishes upon applying a strong parallel magnetic field. These results provide experimental evidence that the 0.7 structure is associated with two conduction channels that have different transmission probabilities.