Effects of decoherence on the shot noise in carbon nanotubes

TL;DR

This paper investigates how decoherence affects shot noise in carbon nanotubes, revealing that finite lifetime of fractional charge modes can still produce detectable signatures of charge fractionalization in noise measurements.

Contribution

It introduces a model showing that decoherence can preserve fractionalization signatures in shot noise despite interactions and impurities.

Findings

Finite lifetime of fractional modes reduces the Fano factor.

Decoherence effects can explain experimental reductions in Fano factor.

Signatures of charge fractionalization remain detectable with decoherence.

Abstract

We study the zero frequency noise in an interacting quantum wire connected to leads, in the presence of an impurity. In the absence of quasiparticle decoherence the zero-frequency noise is that of a non-interacting wire. However, if the collective, fractionally-charged modes have a finite lifetime, we find that the zero-frequency noise may still exhibit signatures of charge fractionalization, such as a small but detectable reduction of the ratio between the noise and the backscattered current (Fano factor). We argue that this small reduction of the Fano factor is consistent with recent observations of a large reduction in the experimentally-inferred Fano factor in nanotubes (calculated assuming that the backscattered current is the difference between the ideal current in a multiple-channel non-interacting wire and the measured current.