Large Magnetic Susceptibility Anisotropy of Metallic Carbon Nanotubes

TL;DR

This study measures the magnetic susceptibility anisotropy of metallic carbon nanotubes, revealing it to be significantly larger than that of semiconducting nanotubes, due to their large orbital paramagnetism and Aharonov-Bohm effects.

Contribution

It provides the first direct measurement of magnetic susceptibility anisotropy in metallic nanotubes and explains the large anisotropy through orbital paramagnetism and quantum effects.

Findings

Metallic nanotubes have 2-4 times greater anisotropy than semiconducting ones.

The anisotropy is explained by large orbital paramagnetism and Aharonov-Bohm effects.

Results challenge the linear diameter dependence prediction.

Abstract

Through magnetic linear dichroism spectroscopy, the magnetic susceptibility anisotropy of metallic single-walled carbon nanotubes has been extracted and found to be 2-4 times greater than values for semiconducting single-walled carbon nanotubes. This large anisotropy is consistent with our calculations and can be understood in terms of large orbital paramagnetism of electrons in metallic nanotubes arising from the Aharonov-Bohm-phase-induced gap opening in a parallel field. We also compare our values with previous work for semiconducting nanotubes, which confirm a break from the prediction that the magnetic susceptibility anisotropy increases linearly with the diameter.