Experimental study of reduced shot noise in a diffusive mesoscopic conductor

We demonstrate that a diffusive narrow wire of a length much longer than the elastic scattering length and the phase-coherence length, but of the order of the energy relaxation length, exhibits shot noise with an intensity lower than the full shot-noise level. At 4.2 K, the reduction factor is shown to vary between 0.2 and 0.45, depending on the width of the wire. The reduction is consistent with recent theoretical predictions.