Very low shot noise in carbon nanotubes
Résumé
We have performed noise measurements on suspended ropes of single wall carbon nanotubes (SWNT) between 1 and 300 K for di erent values of dc current through the ropes. We nd that the shot noise is suppressed by more than a factor 100 compared to the full shot noise 2eI.We have alsomeasured an individual SWNT and found a level of noise which is smaller than the minimum expected. Another nding is the very low level of 1=f noise, which is signi cantly lower than previous observations. We propose two possible interpretations for the strong shot noise reduction: i) Transport within a rope takes place through few nearly ballistic tubes within a rope and possibly involves non integer e ective charges with e 0:3e. ii) A substantial fraction of the tubes conduct with a strong reduction of e ective charge (by more than a factor 50).