Helical modes in carbon nanotubes generated by strong electric fields

TL;DR

This paper demonstrates that strong electric fields can induce helical modes in metallic carbon nanotubes through spin-orbit interaction, with potential control via magnetic fields, expanding understanding of spin-dependent transport in nanotubes.

Contribution

It introduces a method to generate and control helical modes in metallic nanotubes using electric and magnetic fields, derived from a tight-binding model.

Findings

Helical modes exist in metallic armchair nanotubes under strong electric fields.

Applying a magnetic field can induce helical modes in chiral nanotubes.

Selective gapping at Dirac points enables control over helical states.

Abstract

Helical modes, conducting opposite spins in opposite directions, are shown to exist in metallic armchair nanotubes in an all-electric setup. This is a consequence of the interplay between spin-orbit interaction and strong electric fields. The helical regime can also be obtained in chiral metallic nanotubes by applying an additional magnetic field. In particular, it is possible to obtain helical modes at one of the two Dirac points only, while the other one remains gapped. Starting from a tight-binding model we derive the effective low-energy Hamiltonian and the resulting spectrum.