Conduction in Carbon Nanotubes Through Metastable Resonant States

TL;DR

This study investigates how impurities and defects in multi-walled carbon nanotubes influence their low-temperature electrical conductance, revealing quantum interference effects like Fano resonances that significantly alter transport properties.

Contribution

It demonstrates the impact of impurities on quantum interference phenomena in carbon nanotubes, highlighting the role of resonant states in electrical conduction at low temperatures.

Findings

Impurities cause large variations in conductance behavior.

Resonant transmission through discrete states affects conductance.

Quantum interference leads to Fano resonances in nanotubes.

Abstract

We report here on electrical measurements on individual multi-walled carbon nanotubes (MWNTs) that show that the presence or movement of impurities or defects in the carbon nanotube can radically change its low temperature transport characteristics. The low temperature conductance can either decrease monotonically with decreasing temperature, or show a sudden increase at very low temperatures, sometimes in the same sample at different times. This unusual behavior of the temperature dependence of the conductance is correlated with large variations in the differential conductance as a function of the dc voltage across the wire. The effect is well described as arising from quantum interference of conduction channels corresponding to direct transmission through the nanotube and resonant transmission through a discrete electron state, the so-called Fano resonance.