Superconducting diamagnetic fluctuations in ropes of carbon nanotubes

TL;DR

This study detects low-temperature diamagnetic signals in ropes of carbon nanotubes, suggesting the presence of superconductivity evidenced by the Meissner effect, despite magnetic noise from ferromagnetic particles.

Contribution

First direct magnetization measurements showing the Meissner effect in carbon nanotube ropes, supporting their superconducting nature from transport data.

Findings

Diamagnetic signals observed below 0.5K and 80 Oe

Evidence of Meissner effect in nanotube ropes

Superconductivity confirmed through magnetization measurements

Abstract

We report low-temperature magnetisation measurements on a large number of purified ropes of single wall carbon nanotubes. In spite of a large superparamagnetic contribution due to the small ferromagnetic catalytical particles still present in the sample, at low temperature ($T < 0.5K$) and low magnetic field ($H < 80 Oe$), a diamagnetic signal is detectable. This low temperature diamagnetism can be interpreted as the Meissner effect in ropes of carbon nanotubes which have previously been shown to exhibit superconductivity from transport measurements.