Disorder induced transverse delocalisation in ropes of carbon nanotubes

TL;DR

Disorder within carbon nanotubes can induce transverse delocalization, significantly affecting electronic transport by increasing intertube coupling and longitudinal delocalization, as shown through simple models and numerical simulations.

Contribution

This paper demonstrates that disorder within nanotubes promotes transverse delocalization and alters electronic transport in ropes, combining analytical and numerical approaches.

Findings

Disorder enhances intertube electronic transfer.

Transverse delocalization increases sensitivity to boundary conditions.

Longitudinal localization length is increased by disorder.

Abstract

A rope of carbon nanotubes is constituted of an array of parallel single wall nanotubes with nearly identical diameters. In most cases the individual nanotubes within a rope have different helicities and 1/3 of them are metallic. In the absence of disorder within the tubes, the intertube electronic transfer is negligeable because of the longitudinal wave vector mismatch between neighboring tubes of different helicities. The rope can then be considered as a number of parallel independent ballistic nanotubes. On the other hand, the presence of disorder within the tubes favors the intertube electronic transfer. This is first shown using a very simple model where disorder is treated perturbatively inspired by the work in reference \cite{maarouf00}. We then present numerical simulations on a tight binding model of a rope. Disorder induced transverse delocalisation shows up as a spectacular increase of the sensitivity to the transverse boundary conditions in the presence of small disorder. This is accompanied by an increase of the longitudinal localisation length. Implications on the nature of electronic transport within a rope of carbon nanotubes are discussed.