Finite size effects, super-and sub-poissonian noise in a nanotube connected to leads

TL;DR

This paper investigates how finite size effects influence noise characteristics in a carbon nanotube connected to leads, revealing super- and sub-Poissonian noise behaviors and their dependence on voltage and AC modulation.

Contribution

It demonstrates the impact of finite size effects on noise in nanotube transport and proposes zero frequency noise measurement as a diagnostic tool.

Findings

Noise auto-correlation deviates from Schottky behavior at finite size effects.

Super- and sub-Poissonian noise observed as voltage varies.

Stepwise noise derivative behavior indicates finite size effects.

Abstract

The injection of electrons in the bulk of carbon nanotube which is connected to ideal Fermi liquid leads is considered. While the presence of the leads gives a cancellation of the noise cross-correlations, the auto-correlation noise has a Fano factor which deviates strongly from the Schottky behavior at voltages where finite size effects are expected. Indeed, as the voltage is increased from zero, the noise is first super-poissonian, then sub-poissonian, and eventually it reaches the Schottky limit. These finite size effects are also tested using a diagnosis of photo-assisted transport, where a small AC modulation is superposed to the DC bias voltage between the injection tip and the nanotube. When finite size effects are at play, we obtain a stepwise behavior for the noise derivative, as expected for normal metal systems, whereas in the absence of finite size effects, due to the presence of Coulomb interactions, a smoothed staircase is observed. The present work shows that it is possible to explore finite size effects in nanotube transport via a zero frequency noise measurement.