Carbon nanotubes in electric and magnetic fields

TL;DR

This paper develops a low-energy theoretical framework for metallic carbon nanotubes under electric and magnetic fields, revealing how these fields can induce helical conduction modes and influence spin resonance properties.

Contribution

It introduces a comprehensive model incorporating spin-orbit interactions and screening effects, demonstrating control over conduction modes in nanotubes via external fields.

Findings

Electric fields can turn armchair nanotubes into helical conductors.

Magnetic fields can restore helical modes in non-armchair nanotubes.

Rabi frequency in electric dipole spin resonance depends on nanotube momentum.

Abstract

We derive an effective low-energy theory for metallic (armchair and non-armchair) single-wall nanotubes in the presence of an electric field perpendicular to the nanotube axis, and in the presence of magnetic fields, taking into account spin-orbit interactions and screening effects on the basis of a microscopic tight binding model. The interplay between electric field and spin-orbit interaction allows us to tune armchair nanotubes into a helical conductor in both Dirac valleys. Metallic non-armchair nanotubes are gapped by the surface curvature, yet helical conduction modes can be restored in one of the valleys by a magnetic field along the nanotube axis. Furthermore, we discuss electric dipole spin resonance in carbon nanotubes, and find that the Rabi frequency shows a pronounced dependence on the momentum along the nanotube.