Shot noise in carbon nanotube based Fabry-Perot interferometers

TL;DR

This study measures shot noise in carbon nanotube Fabry-Perot interferometers, revealing quantum interference effects, nearly perfect transmission at resonance, and insights into electron interactions and decoherence.

Contribution

It provides the first quantitative analysis of shot noise oscillations in nanotube interferometers, confirming the role of nearly degenerate orbitals and weak backscattering effects.

Findings

Shot noise oscillates with gate voltage due to quantum interference.

At resonance, nanotubes become noiseless with near-unity transmission.

Noise dependence on backscattering current is weaker than expected.

Abstract

We report on shot noise measurements in carbon nanotube based Fabry-Perot electronic interferometers. As a consequence of quantum interferences, the noise power spectral density oscillates as a function of the voltage applied to the gate electrode. The quantum shot noise theory accounts for the data quantitatively. It allows to confirm the existence of two nearly degenerate orbitals. At resonance, the transmission of the nanotube approaches unity, and the nanotube becomes noiseless, as observed in quantum point contacts. In this weak backscattering regime, the dependence of the noise on the backscattering current is found weaker than expected, pointing either to electron-electron interactions or to weak decoherence.