Disorder effects and electronic conductance in metallic carbon nanotubes

TL;DR

This paper investigates how disorder affects the electronic density of states and conductance in metallic carbon nanotubes, revealing a significant conductance reduction mainly due to lattice fluctuations, with effects varying near the Fermi energy.

Contribution

It provides a detailed analysis of disorder effects on conductance in metallic nanotubes using a tight binding model, highlighting the role of lattice fluctuations and electronic state extension.

Findings

Conductance decreases by a factor of 1/2 to 1/3 due to disorder.

Suppression of conductance near the Fermi energy is smaller than in valence/conduction bands.

Electronic states near the Fermi energy are extended, reducing disorder effects.

Abstract

Disorder effects on the density of states and electronic conduction in metallic carbon nanotubes are analyzed by a tight binding model with Gaussian bond disorder. Metallic armchair and zigzag nanotubes are considered. We obtain a conductance which becomes smaller by the factor 1/2 ~ 1/3 from that of the clean nanotube. This decrease mainly comes from lattice fluctuations of the width which is comparable to thermal fluctuations. We also find that suppression of electronic conductance around the Fermi energy due to disorder is smaller than that of the inner valence (and conduction) band states. This is a consequence of the extended nature of electronic states around the Fermi energy between the valence and conduction bands, and is a property typical of the electronic structures of metallic carbon nanotubes.